3-Way JSON Merge
Merge three JSON versions online: base, ours, and theirs. Independent changes apply automatically, so you only resolve genuine conflicts. Free, with no upload.
Files never leave your browser.
About 3-way JSON Merge
Three-input JSON merge with conflict detection: base + ours + theirs, similar to git's recursive merge but at the JSON property level. Non-conflicting edits flow through automatically.
How to use
- Paste the common ancestor (base) JSON into its editor.
- Paste both edited versions into ours and theirs.
- Resolve conflicts property by property; non-conflicting changes are taken automatically.
Try a sample
A package manifest where each side bumped a different field from the same starting point.
What this tool doesn't handle
- Requires a base version; use Merge JSON if you only have two inputs.
- Array semantics default to ordered comparison. Adjust under Options if you need set-style merging.
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.
When should I use 3-way JSON Merge instead of JSON Merge?
Use 3-way when both versions evolved from a known common base, for example a git conflict in package.json. Non-conflicting edits apply automatically, so you only decide the true conflicts.
What counts as a conflict in a 3-way JSON merge?
A property changed on both sides to different values. If only one side changed a property, that change flows through without asking you.
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.