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onDevTools JSON Formatter
What it is
onDevTools JSON Formatter is a browser-based tool for formatting, checking, querying, comparing, and changing JSON. It can pretty-print or minify data, use 2-, 4-, or 8-space indentation, and optionally sort keys alphabetically. It accepts strict RFC 8259 / ECMA-404 JSON as well as JSONC with comments and trailing commas; it does not support JSON5. Schema checks use JSON Schema Draft 2020-12 and identify violations with JSON Pointer paths. Its RFC 9535 JSONPath engine offers wildcards, recursive descent, slices, and filters. Users can compare documents side by side and create a JSON Merge Patch, or flatten and unflatten data and remove null or empty values. A collapsible tree supports full-text search and copying a value or pointer path. The maker says processing runs locally in the browser and JSON is not uploaded. Above about 1 MB or 50,000 nodes, tree navigation and JSONPath can slow noticeably; streaming and JSON Lines are out of scope. Numbers above 2^53 − 1 may lose precision, so 64-bit IDs are recommended as strings. The free plan is free, with no account required.
For and against
For
- Formats with selectable indentation and key sorting
- Checks JSON Schema Draft 2020-12
- Queries with RFC 9535 JSONPath
- Runs listed processing locally in the browser
- Free plan requires no account
Against
- JSON5 is not supported
- Tree and JSONPath can slow on large inputs
- Streaming and JSON Lines are out of scope
- Large numbers may lose precision
The verdict
This web tool brings common JSON formatting, validation, querying, comparison, and transformation tasks together at no listed cost. Consider its large-input slowdown and number-precision caveat when working with sizable documents or large numeric identifiers.
Who it suits
It suits developers working with API responses, configuration files, or production payloads in a browser. It may be useful when schema validation, JSONPath queries, and document comparison are needed together.
Plans and prices
Free
Free online JSON formatting and validation; no account required
Read 7 Oct 2026 · ondevtools.com
On the record
- Diff
- Compares JSON documents side by side and can produce a JSON Merge Patch.ondevtools.com · read 7 Oct 2026
- Formatting
- Pretty-prints or minifies JSON with 2-, 4-, or 8-space indentation and optional alphabetical key sorting.ondevtools.com · read 7 Oct 2026
- Intended audience
- The maker presents onDevTools as a toolkit for developers and says the JSON tool can handle API responses, configuration files, and production payloads in the browser.ondevtools.com · read 7 Oct 2026
- JSON modes
- Supports strict RFC 8259 / ECMA-404 parsing and JSONC comments and trailing commas; JSON5 is not supported.ondevtools.com · read 7 Oct 2026
- JSONPath
- Provides an RFC 9535 JSONPath query engine with wildcards, recursive descent, slices, and filters.ondevtools.com · read 7 Oct 2026
- Large input limit
- The maker says the tree view and JSONPath become noticeably slower above about 1 MB or 50,000 nodes; streaming and JSON Lines are out of scope.ondevtools.com · read 7 Oct 2026
- Maker
- The About page identifies Onur Kat as an SAP Certified SAP Commerce Developer and DevOps Engineer.ondevtools.com · read 7 Oct 2026
- Number precision
- Numbers larger than 2^53 − 1 can lose precision because the parser uses IEEE-754 doubles; the maker recommends representing 64-bit IDs as strings.ondevtools.com · read 7 Oct 2026
- Privacy
- The maker says parsing, validation, schema checks, diffing, and transforms run locally in the browser and JSON is not uploaded.ondevtools.com · read 7 Oct 2026
- Purpose
- Formats, validates, queries, diffs, and transforms JSON in the browser.ondevtools.com · read 7 Oct 2026
- Schema validation
- Validates against JSON Schema Draft 2020-12 and reports violations with JSON Pointer paths.ondevtools.com · read 7 Oct 2026
- Transforms
- Can flatten and unflatten JSON, remove nulls or empty values, and minify output.ondevtools.com · read 7 Oct 2026
- Tree navigation
- The collapsible tree view supports full-text search and copying a node's value or JSON Pointer path.ondevtools.com · read 7 Oct 2026
