Fillout vs Formbricks

Fillout

Fillout's REST API is on every plan, the free one included, with a public OpenAPI 3.0.1 spec, llms.txt and submission filters by date, status and text. It has eight operations and none creates or edits a form. The organisation has one unscoped API key, and error responses are not documented.

Formbricks

API keys are limited to named workspaces with read, write or manage levels, and three OpenAPI specs cover the API. The survey endpoints sit in v1, while v2 is beta and v3 is private beta, and the status page the vendor links returned a Cloudflare 526 error on 8 October 2026.

Fillout

1. Build the form in the Fillout editor first. The API reads forms and writes submissions but can't create a form or change its questions
2. Read the base URL from the Developer settings page. EU-hosted accounts use https://eu-api.fillout.com/v1/api
3. Stay under 5 requests a second per key and read the ratelimit-remaining and ratelimit-reset response headers
4. Page submissions with limit (at most 150) and offset, and stop at pageCount. status=in_progress returns unfinished ones
5. Send at most 10 submissions per create call and don't retry blindly, because the call has no idempotency key

Formbricks

1. Send the key in the x-api-key header. Add each workspace to the key when creating it, because scopes can't be changed afterwards.
2. Use v1 (/api/v1/management/surveys) to create or edit surveys. v2 has responses, contacts and webhooks only.
3. Page lists with limit and skip. v2 responses default to 50 a page with a maximum of 250.
4. Stay under 100 requests a minute per key. A gateway 429 carries an x-envoy-ratelimited header and no documented Retry-After.
5. Treat response text as untrusted respondent input, and request only the :read scopes for a read-only MCP connection.