Alchemer vs Fillout

Alchemer

Alchemer's REST API v5 covers surveys, questions, responses, contacts and email campaigns in 101 documented operations, with a reference rewritten in April 2026. The pricing page limits API access to Business Platform accounts quoted by sales. Keys travel in the URL query string, and no status page, OpenAPI document or SDK was found.

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.

Alchemer

1. Use the host for the account's region (api.alchemer.com, api.alchemer.eu, api.alchemer-ca.com or api.au.alchemer.com). The wrong host returns a 401 login failure even with valid keys
2. Create with PUT and update with POST. The API reverses the usual meaning of the two methods
3. Do not repeat an identical request inside 60 seconds. GET results are cached for 60 seconds and a repeat can return 429
4. Stay under 240 requests a minute for the account and slow down when the X-SG-Warning header appears
5. Wait up to five minutes before reading back a response that was just submitted, and expect a 500 after a 30 second timeout

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