Did you know that the typical online course completion rate is as low as 12.6%?
Let’s be real – “How many Udemy courses have you signed up for and never completed?”.
As a course creator, if your course isn’t engaging enough and doesn’t hold your students accountable through gamification features, you just won’t make the cut.
We’ve got you covered with the best online course platforms where you can host your own training courses.
In this blog post, we’ve picked the platforms based on how well the platform performs in each of the areas:
- Increasing student engagement and interaction
- Student accountability mechanisms
- Community and networking features
- Marketing automation abilities (take Zapier out of the equation!)
What else you need?
These reviews are presented based on my 4-5 years of instructional design experience experimenting with different LMS solutions. 🙌
Let’s get started!
|Pricing starts at
|Podia – Best value for money
|Yes, but basic
|Kajabi – Best for marketing automation ⚙️
|Yes with gamification
|Teachable – Specialist in courses
|Thinkific – A good Teachable alternative
|Yes, but basic
|LearnWorlds – For academic courses
|Yes, but feels old-school
|Passion.io – Mobile-centric platform 📱
|Systeme.io – ClickFunnels + LMS
|$495 for a lifetime
|LearnDash – WordPress-based flexible solution
|No. But BuddyBoss integration
Best online course platforms (cloud-based)
Podia – Best value for money
Podia is an all-in-one platform that allows you to sell your courses, community, digital products, host webinars (through Zoom and YT Live integrations) and more.
- Courses: Podia allows you to host an unlimited number of courses with unlimited bandwidth. It supports various formats for course content, such as text, quizzes, embeds, coaching, and digital files. It also has features like drip scheduling, course completion certificates, and lesson-wide comments to increase engagement.
- Digital product selling: Podia is one of the few platforms that come with Gumroad-like digital product selling ability. It also comes with embedded checkouts ability suitable for you to sell exclusive content right inside your blog (say on WordPress).
- Community: Podia has a basic community feature that allows you to create multiple membership types and gives people access to different community groups based on their membership levels. However, it lacks a mobile app.
- Marketing: For marketing your courses and communities, Podia provides features like coupons, product bundling, and upsells. However, it lacks some advanced marketing functionalities like order bumps, downsells, and marketing automation features that are offered by other tools such as Kajabi.
- Email: One of the good things about Podia is that it has an in-built email marketing feature that allows you to send out one-off broadcasts or set email sequences to be triggered on specific conditions. Also, it supports tags, segments, and decent automation features.
- Website builder: You can use its website builder to design storefronts and landing pages. However, it is not very flexible. It comes with limited blocks, sections, and design options. It feels rigid. You may still need to use platforms like WordPress or Squarespace for designing your landing pages.
Podia has a free plan with limited features such as a full website, community, products, etc., for you to get an understanding of how their platform works. You can draft courses, webinars, and create a free sales page before you’re ready to go live. However, you will be charged an 8% transaction fee when you make a sale on their fee plan.
Their ‘Mover Plan’ which costs $39/month provides you with all the necessary features for a course creator except for webinars, affiliates and the ability to include 3rd party code.
- Simple to use (without a lot of bells and whistles), making it beginner-friendly.
- Really good UI/UX. You’ll love using it.
- Supports selling digital products.
- Comes with email broadcasts, campaigns (sequences), and automations.
- Good value for money (compared to say Teachable).
- Basic community feature
- It lacks a mobile app
- Doesn’t have advanced course features like course compliance and student-level analytics and heatmaps unlike Teachable or even Kajabi.
- The page builder customization options are very limited. You still need to use WordPress
- Lacks advanced automations features (unlike Kajabi).
You can read the complete review of Podia here.
Bottomline:Podia is an all-in-one digital selling platform with a wide range of features. However, it’s almost like a jack-of-all-trades and master of none. Still, you may end up using specialist tools for say website builder and community(based on your requirements). But for the price, Podia offers good value for money.
Kajabi – Best for advanced course creators ⚙
Kajabi is a powerful all-in-one course creation platform with excellent marketing features.
It’s not a course creation platform, but a digital selling platform with marketing automation capabilities. It’s a hybrid between ClickFunnels and Teachable.
- Courses: Apart from basic course features, it also offers advanced specialist features such as course compliance, automated progress tracking, and student-level analytics.
- Community: Kajabi has a feature-rich community module that includes gamification features such as challenges, badges, points, and leaderboards.
- Email marketing: Kajabi provides powerful email marketing software that integrates well with the rest of its features through its automation engine.
- Website builder: Kajabi comes with a robust page builder that allows for the creation of websites, landing pages, and blog posts. It is flexible, with over 40+ blocks, eliminating the need to use WordPress or Squarespace for website building.
- Marketing automation: Kajabi’s marketing automation features allow you to create triggers and workflows based on certain conditions. For example, When a person completes a challenge in the community, send a course completion certificate. The possibilities are endless with Kajabi’s automation feature.
- Mobile app: Kajabi has iOS and Android apps with push notifications and in-app purchases.
When it comes to pricing, Kajabi is very expensive. The pricing starts at $149/mo. You can consider going with annual billing to get 20% OFF. If you think Kajabi is not affordable for you, consider looking at its alternatives.
- There’s really good depth to the features that Kajabi offers you. Like:
- It comes with student-level course analytics and retention graphs
- The community feature is feature-rich and has gamification features
- Their powerful website builder comes with a funnel feature (saving your WordPress and hosting bill)
- The email marketing feature is quite robust and integrates well with its automation engine and other features.
- It comes with coaching support to handle mentorship packages.
- It comes with native webinars (called Kajabi Events)
- Kajabi’s automations are very powerful (saving your Zapier bill)!
- iOS and Android apps (with push notifications and in-app purchases)
- It has some learning curve for beginners as it comes with lots of features (especially automation).
- The pricing is quite high (starting at $149/month)
- Its lowest plan (even at $149/month) limits to only 3 products and 3 pipelines which is very restrictive.
If you’re interested in learning more about Kajabi, you can check out this review.
Bottomline: If you need advanced marketing features with powerful course features, community, automations, funnels, events, etc. Kajabi would be the best choice. The platform is designed with sound systems design principles. It is great for industry leaders and advanced marketers if pricing is not a concern.
Teachable – Specialist in courses
Teachable is a course platform that allows you to create and sell:
- Online courses: It’s a specialist in course creation. It has real depth to features here. For example, it has superior course compliance features like:
- Enforcing video watching
- Enforcing lecture order
- Enforcing quiz completion
- Coaching: If you want to provide more value to your customers, use Teachable’s coaching feature to offer professional one-on-one or small-group coaching.
- Digital downloads: Sell your knowledge in the simplest way possible through Digital Downloads. You can sell: Podcasts, Ebooks, How-to guides, Customizable templates, Music and audio, Spreadsheets, and so much more!
It has some advanced course creation features.
You’ll be able to also see the per-student progress level using Teachable’s unique video analytics feature.
These features help ensure that students actually complete the course which in turn helps your course completion rate.
Unlike tools like Podia or Kajabi, it’s not an all-in-one platform and doesn’t come with communities, email marketing, etc.
Teachable offers a free plan but you need to pay 10% of the transaction fee.
Teachable doesn’t offer any free plan. However, you can opt for a free trial and preview all their advanced plan features for 14 days.
Their basic plan starts from $59/month but also charges you a 5% transaction fee. If you prefer not to pay transaction fees, you can look at some of these Teachable alternatives.
If you want to eliminate the transaction fee and publish up to 50 products, you must choose their pro plan at $159 per month. However, this is not a good value for money, considering that you can get better options at the same price with all-in-one platforms like Podia or even Kajabi.
- It allows you to upload multiple content formats in the same lesson thus enhancing the flexibility to add course content.
- Superior course compliance and student-level course engagement analytics with retention graphs and heatmaps.
- Comes with a “Lesson notes” feature enabling students to take timestamped notes on the lesson videos.
- Teachable’s checkout page design is more conversion-optimized, with guarantee badges and the ability to include order bumps.
- It comes with automated tax compliance and built-in EU VAT tax calculation.
- Even their Basic plan at $59/month, comes with the ability to host max up to 5 products and charges a 5% transaction fee on your sales.
- It lacks a drag-and-drop builder to design the pages and the site. But it has the ability to add simple modules – not like a full-fledged visual website builder.
- Comes with only iOS app for students.
You can read my complete review of Teachable to learn more about it.
Bottomline: Most people end up choosing Teachable’s Pro plan at $159 per month to remove the limitations described earlier. However, if you want access to some specialist course creation features without paying the premium price of tools like Kajabi, and you’re okay with the 5% transaction fee and the limitation of having only 5 published products, you can choose their Basic plan at $59 per month.
Thinkific – A good Teachable alternative
Thinkific is a feature-rich and affordable platform for course creators. It comes with the ability to create courses and communities.
Compared to Teachable, it has some powerful features like:
- Single communities
- Live lessons (integrates with Zoom)
- Advanced course-building features (like randomized quiz banks, prerequisite lessons, members-only website pages, Brillium exams integration, etc.)
Also, it supports more content types than say Teachable. You can add:
- Multimedia files
- Live lessons
- Surveys, and more!
It also supports Adobe Captivate & Articulate Storyline files.
Thinkific has excellent customization options. You have full control over the course player customization. To design your site, it provides 3 themes and you can custom code it using HTML/CSS/Liquid templating.
Thinkific’s free plan is quite limited in that you cannot create an unlimited number of courses. However, unlike Teachable’s Basic Plan, Thinkific does not charge any transaction fees even on its free plan.
Thinkific is an affordable alternative to Teachable. However, if you want more features, such as the ability to offer subscription pricing, additional functionality, and the ability to create unlimited courses, you will need to upgrade to their Basic plan, which costs $49 per month.
- It doesn’t charge any transaction fees even on its free plan, unlike Teachable’s Basic plan.
- It provides advanced course-building features like live lessons, randomized quizzes, exams, private & hidden courses, etc.
- It is a completely white-labelled solution and is suitable for agencies providing instructional design services.
- Ability to create communities.
- The marketing features are pretty basic. There are no funnels or automation features. You may need to hook it up with Zapier.
- It doesn’t handle EU VAT.
Check out our Thinkific is a really good alternative to Teachable. It has almost all the features that Teachable has, but without its downsides such as product creation limitations and transaction fees.
LearnWorlds – For academic courses
LearnWorlds is an online course platform best suitable for academic institutions and educational organizations.
It focuses on student engagement and enhances learning with:
- Interactive videos
- Surveys, and much more.
It has an intuitive drag-and-drop block-based builder. It gives you enough templates and landing pages to design your school.
For marketing, it supports upsells and cross-sells with promotions, coupons, and payment plans. It also has a branded mobile app that is completely white-labelled. The app supports in-app purchases and push notifications.
LearnWorlds’ lowest pricing starts at $29/mo. If you are a professional trainer, you can go with a $99/mo plan and get more features like memberships, subscriptions, blogs, and no transaction fee (for high-volume sales).
- It is a completely white-labelled solution (good if you’re serving corporate clients).
- Has iOS and Android apps with in-app purchases and push notifications.
- Supports upsells, cross-sells, course bundles, etc.
- It supports SCORM compliance, best for universities.
- It has a pop-up builder for lead generation.
- The lowest plan charges a $5 fee per course sale.
- The basic plan lacks powerful features like a customizable course player, question banks, affiliate management, custom certificates, etc.
- To get a completely white-labelled solution, you need to spend $299/mo.
You can read our complete review of LearnWorlds here.
Bottomline: LearnWorlds is the best solution for academic institutions and educators. It provides powerful features to track students’ progress and also to increase their engagement. It even comes with marketing features like upsells, cross-sells, and a pop-up builder to get leads and convert them.
Passion.io – Mobile-centric platform 📱
Passion.io is an online platform that helps people create their own custom-branded apps without having to write any code. You can use it to create apps for your customers, for business purposes, or for teaching.
The app you create with Passion.io will be accessible on many devices, including smartphones, tablets, TVs, and laptops.
You’ll be also provided the option to publish these apps on the App Store and Google Play, where they can be downloaded by anyone.
- Mobile-centric platform
- Includes a built-in messaging tool that sends push notifications to audience segments.
- Includes goal tracking feature
- Supports content scheduling
- Custom welcome screens and sales pages can be designed without the need for external tools.
- It integrates with popular third-party platforms such as Calendly and Typeform, as well as external analytics tools like Google Analytics.
- Customization options are limited, which may be challenging for some users who want to achieve a specific look and feel for their apps. More app building blocks are in development though.
- The lowest plan comes with a transaction fee of 3.9% and is limited to 100 subscribers, 100 videos, and 1,000 push notifications per month.
- Advanced features like custom branding, drip functionality, and community features are only available on the most expensive plan, which costs $297/mo.
We recommend you to checkout Passion.io’s complete review.
Bottomline: Overall, Passion.io is a fantastic platform for creating custom-branded apps that are instantly accessible on any platform without the need for coding. Although it currently has some limitations, it also has a number of unique features that make it worth considering. If you’re serious about student engagement and want to go mobile, go for it.
Systeme.io – ClickFunnels + LMS
Systeme.io is an all-in-one SaaS platform that comes with sales funnels, email marketing, a website builder, LMS, automation, webinars, and an affiliate program. This makes it an affordable alternative to ClickFunnels, Kartra, and Kajabi for course creators. If ClickFunnels had some basic LMS features, it would be Systeme.
Systeme.io has a two-level structure for designing the course curriculum; modules, and lectures inside them.
It also allows you to drip-schedule the content.
Systeme.io does not include many features such as communities, certificates, tests, and course compliance options that Teachable or Thinkific come with.
Although its LMS features are limited, when you combine them with other features like email marketing, sales funnels, webinars, and the ability to set up your own affiliate program, it leads to the emergence of interesting new use cases to create and sell your online courses.
You can read our Systeme.io review to learn more about it.
ThriveCart has recently introduced an LMS tool called, Thrive Learn to create the courses right inside the platform.
It is offered for free to existing users of ThriveCart.
There is a premium version of this called Learn+, which costs an additional fee to unlock extra powerful features.
Both Learn and Learn+ allow everything unlimited (like unlimited courses, unlimited modules, unlimited lessons, and unlimited students).
It has something called behavioural rules that help automate the course tasks. (Refer to the screenshot above to know all the rules available).
The premium features you get with Learn+ include:
- Advanced sequences
- Team Access
- Student import
- Featured content
- CNAME functionality
Teachery is a dedicated course platform that is popular for its simplicity. You can get started with it easily in no time.
You can add video, audio, or text as lessons or sub-lessons. Like Thinkific, you can completely customize the course player to match your brand.
Unlike Teachable or other platforms, it doesn’t come with video hosting. You need to again spend money on Vimeo or Wistia. Or preferably Bunny Stream as it comes with pay-as-you-go billing for video hosting.
For marketing, it supports custom domains, affiliates, coupons, upsells, course bundles, etc.
Teachery’s (review) pricing starts at $49/mo. It doesn’t charge any transactional fees.
Ruzuku is a decent course creation platform that comes with limited features.
It provides course templates for you to create the courses quickly. It allows multiple instructors and managers for each course (best if you are hosting courses with partners). All its plans support unlimited courses, students, storage, and data.
It excels in its student engagement features. I liked the features it offers for student engagement. These include:
- Live (scheduled calendar-based) courses with automatic email notifications.
- It hosts video broadcasts with slides, group chats, and automatic recording.
- It hosts teleconferences with slides, group chats, and automatic recording.
- General course-wide Q&A and forum.
- Discussion questions/prompts for specific activities/content.
The product looks pretty outdated with not a lot of interesting features for me to feature on the top.
Kartra is an all-in-one marketing solution best for selling your digital and physical products. It is not suitable for courses as it is not a dedicated course creation tool. But it gets the job done with its Kartra Videos tool.
With Kartra Videos, you can sell your individual videos or training (series of videos).
It provides unlimited hosting eliminating the need for external tools like Vimeo or Wistia.
The best thing about Kartra Videos is its video engagement features. You can add social shares, call to action, show controls, show the playback speed, tag the leads based on video watch duration (which you can automate further), and much more.
Kartra provides rich video analytics to see how students are engaging with your videos.
The platform also has funnel-building functionality, which is a great feature to have within an LMS platform as it helps streamline the course marketing process.
Kartra (review) is a cheaper alternative to Kajabi or ClickFunnels, offering campaigns, powerful email marketing, and a visual automation builder. The price starts at $119/month or less with annual billing, which includes a 25% discount.
WordPress-based course hosting platforms
LearnDash – WordPress-based flexible solution
LearnDash is a WordPress-based LMS that is highly flexible and allows for a high degree of customization.
As a self-hosted solution, LearnDash does not come with video hosting built-in, so users will need to utilize an external video hosting platform like Vimeo or Wistia.
But it does come with various features like:
- Drag & drop course builder (with drip feed)
- Student-level course progress tracking (with Propanel)
- Advanced quizzing
- Assignment management
- Flexible prerequisites (similar to course compliance)
The platform is highly customizable, with full control over course player customization and the ability to integrate other plugins like Elementor, CartFlows, Gamipress, and WooCommerce for better design and marketing flexibility.
Also, it supports Zapier integration.
However, as with any other WordPress-based solution, LearnDash requires a certain level of technical knowledge and skills to set up and manage effectively.
Overall, LearnDash is a great choice for those who want a powerful and flexible online course platform. There are definitely technical hurdles to overcome, but the cost is reasonable compared to other popular course platforms out there.
- Ability to productively reuse topics and lessons across multiple courses
- Drip-feed functionality to prevent students from binge-watching courses
- Video progression support to hold students accountable
- Highly customizable and comes with various add-ons.
- Flexible integration with other WordPress plugins like Elementor for better design and customization.
- Requires technical knowledge and skills to set up and manage effectively.
- Similar to any other WordPress plugins, the plugin conflicts and tech problems are a thing!
- Doesn’t have direct compliance with SCORM or xAPI
- No free trial available
Check out LearnDash’s complete review if this is something you’re looking for.
Bottomline: LearnDash is a great choice for those who want a powerful and flexible online course platform based on WordPress at a reasonable cost. It requires good technical skills to even get started, but it provides unparalleled flexibility by plugging right into the WordPress ecosystem.
TutorLMS is one of the most popular WordPress LMS plugins. It is simple to use and provides a lot of features for creating, managing, and selling online courses.
Some of its key features are:
Although TutorLMS is cheaper than LearnDash, as it is a relatively new plugin, there are fewer features, integrations, and third-party add-ons available. All the features available in TutorLMS are also available in LearnDash, plus more (mainly due to integrations with established players).
But needless to say, TutorLMS feels fresh, and I really liked the UI/UX of the front-end drag-and-drop builder – it’s one of the cleanest I have seen.
LifterLMS is one of the feature-rich WordPress LMS plugins that offers powerful features. These include – multi instructor, course export, discussion areas, course reviews, quizzes, quiz timers, content dripping, etc.
For marketing, it supports upsells, coupons, bundles, pre-selling, affiliates, and much more.
For student engagement, it supports:
- Achievement badges
- Personalized email
- Social learning
- Private coaching
- Text messaging
It also supports memberships for you to earn recurring revenue. The membership features include:
- Sitewide memberships
- Course bundles
- Automatic enrollment
- Content Restrictions
- Members-only pricing
- Private group discussion
- Members-only forums
- Bulk course enrollment
If you compare LifterLMS with LearnDash, LifterLMS is more expensive but it offers a free plugin to get started. Also, LearnDash is more popular than LifterLMS.
Course platforms for students
Udemy is an online learning platform that offers courses on a wide range of topics for learners of all levels. The platform boasts over 155,000 courses taught by expert instructors, making it one of the largest and most diverse learning platforms available.
For learners, Udemy provides an opportunity to learn new skills or improve existing ones, all from the comfort of their homes. The courses are designed to be engaging and interactive, with a variety of resources such as videos, quizzes, and assignments to keep learners engaged.
It also offers a range of features that make it an attractive option for businesses and organizations looking to upskill their employees. Additionally, Udemy for Business provides a centralized platform where managers can track employee progress and assign courses accordingly.
- A wide range of courses available on diverse topics
- Courses are engaging and interactive, with a variety of resources to keep learners engaged
- Easy course customization for businesses and organizations
- Udemy for Business provides a centralized platform for employee upskilling
- The quality of courses can vary depending on the instructor
- No direct interaction with instructors
- Certificates of completion lack credibility compared to other options like Coursera
- Courses are not accredited, which may be a drawback for learners seeking formal recognition
Udemy offers both free and paid courses, with prices ranging from as low as $9.99 up to $199.99. The platform also offers a subscription-based service, Udemy for Business, that starts at $360 per user per year.
Bottomline: Udemy can be a helpful platform if you’re just starting out as an online course creator. Since its revenue share is very high, to create a sustainable business, you’ll eventually need to build your own audience and brand.
Skillshare is an online learning platform offering courses on design, photography, video, writing, and more.
Its affordable and accessible courses are taught by experts in their field.
The platform offers a wide variety of courses suitable for beginners and professionals alike.
However, some courses may lack depth, and the platform does not offer certification upon completion.
If you’re looking for more in-depth courses or certification, Udemy or Coursera may be better options.
- Affordable and accessible courses
- Courses taught by experts in their field
- Wide variety of courses to choose from
- Some courses lack depth and may not be suitable for advanced learners
- Limited interactivity with instructors
- No certificates or degrees are offered upon completion
Bottomline: Skillshare is a great platform for creative instructors, but it may not be the right fit for technical or business-focused topics. Unless you have a huge audience, you can’t earn good money from their royalties system. It’s a volume game.
If you’re looking for a way to boost your skills in math, science, and computer science, look no further than Brilliant.org. With interactive lessons that are both fun and challenging, Brilliant can help you build the quantitative skills you need to succeed in any field.
I really liked their interactive classes on computer science, especially Artificial Intelligence. It helped me understand how AI is inspired by our human brain, and how it is used to create better search algorithms.
It really helps students in STEM fields learn the foundational skills from first principles (bottom-up approach), and then apply them in creative ways. It comes with 60+ bite-sized courses to expedite your learning process.
One more thing I really liked is how it challenges you with strategic problems and when you solve them, you not only improve your problem-solving ability but also increase your understanding of the concepts.
After using Brilliant, there’s no going back to old theoretical explanations.
Coursera is an online education platform that offers courses from universities all over the world. Some top universities that offer online courses through Coursera are Columbia University, the University of Pennsylvania, and Princeton.
With more than 5,300 courses, it offers a wide range of subjects, from business and management to science and technology. Take courses taught by experts in your field or explore topics of particular interest to you.
Some of the most popular courses are:
- Machine Learning from Stanford University.
- Learning How to Learn: Powerful mental tools to help you master tough subjects from Deep Teaching Solutions.
- Foundations of Project Management from Google.
- English for Career Development from the University of Pennsylvania.
- Programming for Everybody (Getting Started with Python).
Plus, many of the courses are free. You just need to sign up on the Coursera website, and you can get started right away. But if you need a certificate to show for your work, you’ll have to pay a fee.
Pluralsight is the perfect place to learn about technology, offering over 7,000 courses from 1,500 instructors, including experts from Google and Microsoft. The self-assessment feature helps you find the right course for you.
Here are the top features I liked the most with Pluralsight especially compared to Udemy:
- Paths: Curated selection of courses based on interests and weaknesses, with progress insights on your own personalized dashboard.
- Flow: Visibility into your work/course progress with the team for immediate feedback and accountability.
- Skill Assessment: Test to identify the skills you are lacking in and recommend courses.
- Cloud Labs: Pre-configured cloud station for practising learnings from courses (for cloud computing).
On the other hand, Udemy courses are just pre-recorded videos (with some quizzes, of course), making proactive student engagement optional.
When it comes to pricing, you need to pay $19 per month to get unlimited access to Pluralsight. Compared to it, Udemy feels quite cheaper (especially with those $10 coupons).
But if you plan on taking multiple courses on a monthly basis, Pluralsight can save you more money.
LinkedIn Learning (formerly Lynda) helps businesses and professionals develop the right skills (mainly soft skills & professional skills) to build their careers. With over 27 million users and 17,000+ courses, it is one of the largest online course providers.
It recommends courses based on people’s roles, learning activities, skills, and more. It has a Q&A section to increase the user’s engagement.
To access the quality of the courses, you can sign up for its one-month free trial. If you are keen to adapt to new skills and want to advance in career growth, LinkedIn Learning is the best to go with.
Khan Academy helps students learn various academic subjects like math, economics, computer science, history, etc. It is a nonprofit organization dedicated to providing a free, world-class education to anyone.
Students can study independently outside of the classroom using exercises, instructional videos, and a personalized learning dashboard. But the one thing students hate about this platform is its reward and punishment feature for tests/quizzes (punishing will demotivate the students and prevent them from retaking the tests).
If you are genuinely interested in learning the concepts to grow further in your academics, Khan Academy would be the best choice.
This is all about the best online course platforms. For course creators, Teachable would be the top course platform, if you want a SaaS solution.