What this tool does
Compare two JSON files or snippets online. See added, removed, changed, and type-changed fields in a clear JSON diff.
- Compare two API responses before and after a backend change.
- Check which feature flags were added or removed in a config file.
- Review whether an LLM JSON output changed field types between prompts.
JSON Compare and Diff Tool
| Type | Path | Old | New |
|---|---|---|---|
| Run a comparison to see differences. | |||
When this tool is a good fit
JSON Compare and Diff Tool helps when you need added, removed, changed, and type-changed fields from two JSON objects or arrays that should be compared. It is most useful for finding differences between API responses, config versions, generated JSON, and before-and-after payloads. The notes below focus on the settings that matter, the checks worth doing before you export, and the limits that tend to cause mistakes.
- Takes two JSON objects or arrays that should be compared.
- Lets you adjust which payload is baseline, whether arrays are order-sensitive, and what differences matter.
- Calls out what to review: missing fields, changed types, null values, and nested object differences.
- Produces added, removed, changed, and type-changed fields.
- Fits common jobs such as finding differences between API responses, config versions, generated JSON, and before-and-after payloads.
Example jobs
- Compare two API responses before and after a backend change.
- Check which feature flags were added or removed in a config file.
- Review whether an LLM JSON output changed field types between prompts.
How to use JSON Compare and Diff Tool
- Prepare two JSON objects or arrays that should be compared.
- Set which payload is baseline, whether arrays are order-sensitive, and what differences matter before running the tool.
- Generate or process the result, then review missing fields, changed types, null values, and nested object differences.
- Copy, export, or download added, removed, changed, and type-changed fields.
- Run a second pass if the destination system, document, or workflow has stricter requirements.
What to know before you use it
- Both inputs are parsed as JSON in the browser.
- Objects are compared by field path; arrays are compared by index unless array-order ignore is enabled.
- The report separates added, removed, changed, and type-changed values.
- JSON diff works best after both inputs are valid JSON, not JavaScript object literals or partial fragments.
- Type changes such as string to number can be more important than value changes in API contracts.
Checks and edge cases
- Format both payloads first if they came from logs or minified responses.
- Use schema validation after comparing if the new payload must satisfy a formal contract.
How your data is handled
This tool works in your browser. Toolumina does not upload or keep the content you enter here.
FAQ
Does this upload my JSON?
No. Parsing and diffing are performed locally in your browser.
Can it compare arrays?
Yes. Arrays are compared by index, with an optional simple sort for primitive array values.
Why is this different from a text diff?
This tool compares parsed JSON values, so formatting and whitespace do not create false differences.