Highlight JSON Syntax

Raw JSON is easy to write and surprisingly hard to read. Keys, strings, numbers and punctuation all blur together, and the larger the payload the quicker your eyes lose their place. Highlight JSON Syntax fixes that by colour-coding every part of the structure — keys, string values, numbers, booleans and null — so you can navigate a document by colour instead of squinting at quotes.

Switch between a dark theme for comfortable on-screen reading and a light theme for printing or embedding in documentation. Line numbers give you precise anchors for code reviews and bug reports, and the colourised view can be copied, downloaded as a self-contained styled HTML file, or sent to a printer. Because tokenising runs entirely in the browser, even confidential API responses never leave your machine.

• Class-aware colourising: keys, strings, numbers, booleans, null and punctuation each get their own colour.
• Dark and light themes: switch for screen reading versus printing and embedding.
• Toggleable line numbers: reference exact lines or produce clean snippets.
• Escaping-safe output: all text is HTML-escaped before colourising, so special characters never break the markup.
• Token-based robustness: even malformed JSON is colourised so you can inspect the problem.
• Download as styled HTML: a self-contained file with the stylesheet, ready for wikis and docs.
• Copy or print: grab the highlighted view or send it to a printer / PDF.
• Live updates: re-colourise as you type with the live toggle.
• Private by design: all processing happens locally.

1. Paste your JSON or load it from a file.
2. Pick a theme — dark for screens, light for print and embedding.
3. Toggle line numbers on when you need to cite locations.
4. Review the colourised output in the panel.
5. Copy the highlighted markup or download the standalone styled HTML file.

Example 1 — Documentation. Colourised JSON reads far better in API docs than monochrome blocks. Download the styled HTML and embed it directly.

Example 2 — Code review. Highlight a config or payload before review so reviewers can see structure and spot misplaced commas or unquoted keys without counting braces.

Example 3 — Debugging feeds. A malformed JSON feed is easier to inspect when the offending region is colourised; combine with the validator for line-and-column diagnosis.

Example 4 — Presentation. For talks and internal training, the dark theme with line numbers turns a raw export into a readable walkthrough.

• Structural clarity at a glance — colour does the scanning for you.
• Better documentation — styled output you can embed unchanged.
• Sharper reviews — reviewers focus on structure, not syntax.
• Print-ready — light theme and print CSS give clean hard copies.
• Free and private — local tokenising, no uploads.