Underlayer vs Coassemble

The short version

Side by side

How each one charges

This is the difference most teams will feel first. Coassemble publishes its prices — unusual in this category, and to its credit — and meters usage by identified recipients: people you train and name, 600 a year on its Build plan, with a separate allowance for anonymous views. Every plan is a 12-month agreement.^[2]

Underlayer meters course views: a learner opening a course and reaching its first screen. With a signed identity, the same learner coming back to the same course within 30 days is still one view. Build includes 25,000 views a month for $149 billed monthly, and extra views are $9 per thousand rather than a plan change. You can start month-to-month and stop whenever you like.

The two units are not the same thing, so compare them against your own numbers: if you train a few hundred named people a year, both fit; if thousands of users each open a course or two, per-view pricing usually costs less; and if you want one fixed yearly contract, Coassemble's model is built for it. The Underlayer pricing page has a calculator for your volume.

Building and embedding

Day to day, building on either feels similar. Both give you a REST API that covers the course lifecycle, webhooks for completions, a player you embed with a signed URL, and a builder you can embed for users who author content themselves.^[1][4] Both let an AI client like Claude or Cursor drive the platform over MCP.^[6]

Underlayer's content model is deliberately small — a course is screens, a screen is blocks, and there are 39 block types — and every one of them is documented with a working example in the block reference. The quickstart goes from an API key to a finished course with plain curl.

Where Coassemble is ahead

• Embeddable analytics. Coassemble ships an analytics component alongside the player and builder.^[1] Underlayer gives you the data through the API and webhooks; the charts are yours to draw.
• Self-hosting and dedicated deployments on its Partner plan.^[2] Underlayer is hosted only.
• Multi-SCO packages — a whole collection exported as one SCORM package.^[2]
• AI fidelity controls — verbatim, structured or adaptive generation from source documents.^[2]

Where Underlayer is ahead

• No annual commitment. Monthly billing from $149, cancel whenever; yearly is a discount, not a requirement.
• Per-view pricing with a published overage rate, so a spike in usage costs a known amount and nothing throttles or switches off.
• A security page that lists what we don't have. /security says plainly that there is no SOC 2 report yet, so a questionnaire won't find it for you later.
• Everything exportable on every plan — courses as JSON and SCORM, learner records as CSV — including the free sandbox.

Which one should you pick?

If your procurement process expects a yearly contract, you need self-hosting, or you want analytics components out of the box, Coassemble is a strong choice and the closer fit. If you would rather start small, pay monthly and let the bill follow how many courses actually get opened, try Underlayer's free sandbox — it has every block, the API and MCP.