What is RFC 7396 (JSON Merge Patch)?

RFC 7396 defines a simple format for describing a partial update to a JSON document: each key in the patch overwrites the same key in the target, except null which deletes the key. Object values recurse. It's deliberately simpler (and more limited) than RFC 6902 JSON Patch.

How is JSON Merge Patch different from JSON Patch (RFC 6902)?

JSON Patch (RFC 6902) is an array of explicit operations: add, remove, replace, move, copy, test. JSON Merge Patch is a single document that mirrors the target's shape — null deletes, anything else overwrites or recurses. Merge Patch is easier to read and write but can't express 'add to an array' or 'replace at a path'. Use Merge Patch for HTTP PATCH on document-shaped resources; use JSON Patch when you need precise array operations.

How do I delete a key with Merge Patch?

Set the key's value to null in the patch. The result will not contain that key. This is the one corner case where Merge Patch differs from a naive deep merge — null in the patch means 'delete', not 'set to null'. To actually set a value to null, you can't with Merge Patch (use JSON Patch instead).

Arrays are replaced wholesale. There's no way to merge array items, append, or remove a single element via Merge Patch. If the patch has an array, the target's array (if any) is fully replaced. For element-level array edits, use JSON Patch (RFC 6902).

What if the target is not an object?

If the patch is not an object (e.g. a string, number, or array), the result is just the patch — the target is fully replaced. Per RFC 7396, Merge Patch only does deep recursion for objects.

Where would I use this in production?

HTTP PATCH endpoints on document-shaped resources (Kubernetes admission webhooks, REST APIs that follow the JSON Merge Patch convention), config-update workflows, edit-then-save UIs that send only the diff, or any 'apply this delta' flow that doesn't need precise array operations.

Is my JSON sent to a server?

No. Both target and patch stay in your browser. Safe for production payloads, internal API contracts, and anything containing secrets.

Can I round-trip a Merge Patch?

Not always. Because null means delete (not 'set to null'), Merge Patch is lossy for documents that legitimately contain null leaves. If your target has null values you want to preserve, use JSON Patch instead — Merge Patch can't faithfully describe 'change this null to a non-null value' as a delta.

JSON Merge Patch — Free Online (RFC 7396)

Apply a JSON Merge Patch (RFC 7396) to any JSON document. Null deletes, objects merge recursively, anything else replaces. Browser-based.

Apply an RFC 7396 JSON Merge Patch to any JSON document. The patch mirrors the target's shape: null deletes, objects recurse, anything else replaces. Built for HTTP PATCH endpoints, Kubernetes-style strategic merges (the simple variant), and edit-then-save UIs that send a delta instead of the whole doc.

Need a structural diff instead? JSON Diff. Schema validation? JSON Schema.

Indent

Target JSON

Merge Patch (RFC 7396)

Result

How to Apply a JSON Merge Patch (RFC 7396)

Paste your target JSON
The current document you want to modify — could be a config, an API resource state, or any JSON value.
Paste the Merge Patch
An RFC 7396 patch document. Keys with non-null values overwrite or recurse; keys with null delete the field.
Click Apply Patch
PDFFlare returns the patched JSON. Copy and ship.

When Do You Need JSON Merge Patch?

HTTP PATCH endpoints: Many REST APIs accept the JSON Merge Patch content type (application/merge-patch+json). Build the patch document, apply it locally to verify the result before sending the request.

Kubernetes-style admin tools: Internal admin tooling that expresses changes as merge patches. Apply the patch in dry-run mode here to confirm the resulting document before committing.

Edit-then-save UIs: Your UI computes a delta from the original document and sends only what changed. Apply the delta against the original here to verify it produces the expected final state.

Config-update pipelines: Helm / Kustomize-style overlays that express overrides as a delta. Resolve the delta against the base config before committing the merged result.

Why Use PDFFlare for JSON Merge Patch?

RFC 7396 Compliant

Strict spec semantics: null deletes, objects recurse, arrays and primitives replace wholesale. No surprises at runtime.

Per-Pane Error Highlighting

Bad JSON in target vs patch is reported separately with line numbers — no guessing which pane is malformed.

100% Browser-Based

Both documents stay on your device — safe for production payloads.

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Frequently Asked Questions About JSON Merge Patch

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