TOOLOG TOOL
JSON Merge | Combine Files, JSONL Logs, Arrays, Objects, and Remove Duplicates
Merge multiple JSON files, pasted API responses, and JSONL logs in your browser. Concatenate arrays, merge object keys and shared arrays, count removed duplicates, review key conflicts, choose pretty or minified output, copy results, and download merged.json.
Select up to 50 JSON files (20 MB total). Files are processed only in this browser.
No pasted JSON yet.
Use this for quick API snippets, copied console logs, or JSONL exports. File uploads and pasted JSON can be merged together.
Upload multiple JSON files with similar format and merge/download them at once.
Download merged.jsonWhen should you use JSON Merge?
Use JSON Merge when split JSON files with similar schema need to be combined quickly.
Examples: paged API exports, chunked logs, and batch output files.
It is useful when you saved API responses page by page or need to turn several batch outputs into one merged.json without uploading private data elsewhere. For smaller snippets, paste JSON directly instead of saving temporary files, then test the same array merge or object merge behavior. JSONL logs can also be parsed line by line and merged locally, with empty lines and full-line // comments skipped.
Why this tool was refreshed today
Recent quality passes focused on link-list-cleaner, average-speed-calculator, cafe-work-seat-simulator, blog-banned-word-checker, image-upscaler, case-converter, and grocery-budget-checker, so this update avoids repeating the same tool.
json-merge was selected because it has several failure-prone input paths: file upload, direct paste, JSON parsing, large-size limits, and object-key conflicts. It also matches a clear data-work search intent for people trying to combine JSON files, merge arrays, or test pasted API responses locally.
Key features
- Multi-file JSON upload
- Direct paste input for API responses and log snippets
- Auto mode detects array/object structure
- Manual modes: array concat, object key merge, wrap roots into array
- Shared-array concatenation for objects such as
{ "items": [...] } - JSONL paste mode for one JSON value per line
- Pretty printed or minified output style
- Preview + copy result +
merged.jsondownload - Optional array deduplication count + object key conflict count
- Clear errors for invalid JSON, incompatible manual modes, and excessive file size
- Individual selected-file removal and pasted JSON size guidance
- Sample data to test the merge behavior before choosing files
How to use
- Upload multiple JSON files.
- If you do not have files, paste JSON text directly. Use a line containing only
---between multiple documents, or enable JSONL mode and paste one JSON value per line. - Remove any selected file you do not want to include, and check the pasted-size message if you added manual JSON.
- Pick a merge mode (default: Auto).
- Choose Pretty printed or Minified output.
- Click Merge JSON.
- Review, copy, or download the result.
Notes
- In object-merge mode, duplicate keys are overwritten by later files.
- Manual object-merge mode requires every file root to be a JSON object. Incompatible structures are rejected with an error.
- Array deduplication compares objects with sorted keys, so
{ "a": 1, "b": 2 }and{ "b": 2, "a": 1 }count as the same item. - To protect browser memory, each run accepts up to 50 files with a combined size of 20 MB.
- Uploaded files and pasted JSON share the same 20 MB total limit.
- JSONL mode skips empty lines and lines that start with
//, but trailing comments are not valid JSON and will be reported as parse errors. - If no files or pasted JSON are present, the merge button stays disabled and the page shows an empty-input message.
- Uploaded files and merged results stay in your current browser and are never sent to a server.
Related tools
- Link cleanup: Link List Cleaner
- Text length check: Text Counter
- Key/style cleanup: Case Converter