Compare Two cURL Commands and API Responses

Example: comparing two API responses

This example compares two requests to a public test API, JSONPlaceholder. The only difference between the commands is the item ID. The responses are simplified.

$ curl -X GET "https://jsonplaceholder.typicode.com/todos/1" \
    -H "Accept: application/json"

{
  "userId": 1,
  "id": 1,
  "title": "delectus aut autem",
  "completed": false
}

$ curl -X GET "https://jsonplaceholder.typicode.com/todos/4" \
    -H "Accept: application/json"

{
  "userId": 1,
  "id": 4,
  "title": "et porro tempora",
  "completed": true
}

What the comparison reports

• id changed from 1 to 4.
• title changed from "delectus aut autem" to "et porro tempora".
• completed changed from false to true.
• userId is unchanged.

You can load this example into the form above with Load example.

Compare headers, query parameters and request bodies

The most useful cURL comparisons keep the endpoint the same and change one part of the request. DiffFind runs both commands and shows how the responses differ, so you can see what a header, a query parameter or a request body actually changes.

Illustrative example: one header changed

$ curl "https://api.example.com/v1/plans/pro" \
    -H "Accept-Language: en"

{
  "id": "pro",
  "name": "Pro plan",
  "currency": "USD",
  "price": 29
}

$ curl "https://api.example.com/v1/plans/pro" \
    -H "Accept-Language: de"

{
  "id": "pro",
  "name": "Pro-Tarif",
  "currency": "EUR",
  "price": 27
}

The comparison reports name, currency and price as changed and id as unchanged. This API and its responses are made up for illustration.

Lexical and semantic comparison

Lexical comparison identifies exact additions, removals and changed values between the two responses. It is deterministic: the same inputs always produce the same result.

Semantic analysis explains what the changes mean, for example whether a changed value is cosmetic or likely to affect behavior. Read more about semantic comparison.

The deterministic comparison remains the source of truth. AI analysis is optional and supplements the exact diff; it never replaces it.

Use cases

• Compare development and production responses.
• Compare API versions.
• Validate changes following a deployment.
• Detect regression issues.
• Compare requests with different headers, parameters or payloads.
• Compare structured JSON responses with JSON Compare.

Supported cURL features

• GET, POST, PUT, PATCH and DELETE requests
• Headers
• Authentication, using headers such as Authorization
• Query parameters in the URL
• JSON request bodies
• Structured API responses

cURL comparison supports complete HTTP request definitions. If you only need to compare two URLs, use URL comparison instead. To automate comparisons, see the REST API and API comparison.

Related tools

Working with saved payloads? Try JSON Compare or XML Compare, or compare live endpoints with URL Compare. For meaning rather than exact wording, see Semantic Diff. Prefer to compare on your computer? DiffFind Desktop for macOS and Windows runs locally and is free to use; see the download options. You can also open the DiffFind application directly.