Merge JSON
Merge two JSON files online. Review every differing property, pick the value to keep, and export clean, well-formed JSON. Free and private, with no upload.
Files never leave your browser.
About JSON Merge
Resolves differences between two JSON documents at the property level, letting you pick which side wins per branch. Output is well-formed JSON, regenerated from the merged data.
How to use
- Paste or load both JSON documents into the left and right editors.
- For each differing property, click the side whose value should win.
- Copy or download the merged JSON once every conflict is resolved.
Try a sample
Editor settings with overlapping changes. A familiar two-way merge.
What this tool doesn't handle
- Two-way merge has no shared ancestor. Use 3-way JSON Merge if you started from a common base.
- Arrays merge as whole units; you cannot pick element-by-element across sides.
Frequently asked questions
Do my files ever leave my browser?
No. Every comparison runs locally in your browser. Nothing you paste, drop, or load is uploaded to a server; the tool keeps working even if you go offline after the page loads.
Is this tool free to use?
Yes. All DiffResolver tools are free, with no account, sign-up, or installation. Because processing happens on your device, there are no server-imposed usage limits.
What does the merged output look like?
Consistently formatted JSON regenerated from the merged data: your chosen value for every conflicting property, and the shared values everywhere else. Input formatting is not preserved.
Can I merge arrays element by element?
No. An array is kept or replaced as a whole unit. If you need element-level control, take the closer side and edit the exported result.
Is there a file size limit?
No server limit applies, because nothing is uploaded. The memory of your device sets the practical limit. Above 10 MB for text, 40 MB for images, 100 MB for documents, or 500 MB for archives, the tool warns you that the work can be slow, but it never blocks the file.
Does this tool work offline?
Yes. The browser keeps a copy of the tool after the first visit, so a page you opened before still works without a network. You can also install DiffResolver as an app from the browser menu. Installation stays optional; the site works the same in a normal tab.
Where is my data stored?
Your files are stored nowhere. They stay in the memory of the page and are gone when you close the tab. Only what you save yourself stays in this browser: a snapshot, your tool options, and your theme. To remove it, open Settings and select Clear all local data.