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thebiglabasky merged 1 commit into from
Jul 27, 2026
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Clarify binary response handling for API checks #452

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20 changes: 11 additions & 9 deletions detect/synthetic-monitoring/api-checks/configuration.mdx
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Expand Up @@ -182,10 +182,9 @@ For more details, see our documentation on [Assertions](/detect/assertions).

## Responses

In almost all cases, you have full access to the HTTP response for assertions. We also store the full response
for later retrieval and triaging issues.

Response bodies are limited to a size of 25MB. Responses over this size will trigger a check failure.
In almost all cases, you have access to the HTTP response for assertions. Checkly reads up to 25MB of the response
body. For larger responses, only the first 25MB is available to assertions and teardown scripts. The response body
stored with the result can be truncated further to fit result-size limits.

Additionally, if your API responds with a binary type body, i.e. a PDF or video file, we scrub the body and replace
it with a short text saying that we scrubbed it. We determine the body content type by looking at the `Content-Type`
Expand Down Expand Up @@ -217,11 +216,14 @@ This list shows all content types that we scrub from the response data.

### Asserting on binary response bodies

Adding a **Text body** assertion to a check opts it out of binary scrubbing entirely: the assertion runs against
the real response bytes, and the stored result displays those same bytes instead of the scrubbed message. This is
useful when a server labels a textual payload with a binary content type, such as `application/octet-stream`. The
assertion's *Actual* value is truncated to 10KB for display, and stored response bodies remain subject to the size
limits above. Checks without a Text body assertion keep the scrubbing behavior described in this section.
Adding a **Text body** assertion disables binary scrubbing for the entire check. The assertion, teardown scripts,
and stored result receive the response body instead of the scrubbed message. Use this when a server labels a textual
payload with a binary content type, such as `application/octet-stream`. This does not decode binary formats such as
PDF, ZIP, audio, or video files.

The assertion evaluates the response body up to the 25MB limit above. Its *Actual* value is truncated to 10KB for
display, and the stored response body remains subject to result-size limits. Checks without a Text body assertion
keep the scrubbing behavior described in this section.

## Additional Settings

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