JSON Formatter
Format, validate and explore JSON in a fast tree view, plus nine more developer utilities: Base64, URL, HTML entities, JWT, timestamps, UUIDs, hashes, CSS and number bases.
- H Press H in the popup
- Runs in your browser
- Opens in its own window
A JSON formatter and nine more tools developers use every day
JSON Formatter opens in its own window with ten small tools that every developer reaches for several times a day. No more pasting API responses or tokens into random websites: everything runs locally in your browser, so private data stays private.
Format, validate and explore JSON
Paste JSON to format it with clean indentation, minify it to a single line, or validate it and see exactly where it breaks. Switch the output from Text to Tree to explore it as collapsible branches.
The tree is built for real-world data. It reads the JSON text directly, so very large numbers keep every digit, duplicate keys all show up, and the original key order is kept. Long arrays are grouped in ranges, so even a list of 60,000 records opens quickly, and search jumps straight to a match deep in the document. Copy the path, the value or the JSON of any node with one click.
Nine more utilities in the same window
- Base64: encode and decode text.
- URL encoder and decoder: encode, decode and break a URL into its parts.
- HTML entities: encode and decode special characters.
- JWT decoder: read a token’s header and payload and check when it expires.
- Unix timestamp converter: turn timestamps into readable dates and back, with the current time one click away.
- UUID generator: create UUIDs one at a time or in bulk, and validate existing ones.
- Hash generator: MD5, SHA-1, SHA-256 and SHA-512 for any text.
- CSS formatter: format or minify CSS.
- Number base converter: binary, octal, decimal and hexadecimal.
Why keep these tools local?
API responses, access tokens and JWTs often contain personal data, keys or session details. Pasting them into an online formatter sends them to someone else’s server. JSON Formatter never sends anything anywhere: decoding, hashing and formatting all happen on your computer.
Who uses it
- Back-end and front-end developers reading API responses and debugging payloads.
- QA engineers checking test data and tokens.
- DevOps and support teams decoding JWTs and timestamps from logs.
Tip: Switch the JSON output to Tree and use search to jump straight to a key in a large response.
How to format and validate JSON
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Open the window
Click JSON Formatter in DevToolkit (or press H). It opens in its own window.
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Pick a tool and paste
Choose JSON or another tool, such as Base64 or JWT, and paste your text.
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Format and copy
Format, minify or validate, explore the tree view, and copy the result.
What you can do with JSON Formatter
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Format, minify, validate
Clean JSON in one click, with clear error messages.
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Fast tree view
Searchable, with ranges for huge arrays and exact numbers.
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Copy path or value
Grab the path, value or JSON of any node.
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JWT decoder
Header, payload and expiry at a glance.
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Encoders and converters
Base64, URL, HTML entities, timestamps and number bases.
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UUIDs and hashes
Generate UUIDs and MD5 or SHA hashes locally.
JSON Formatter questions
Is JSON Formatter free?
JSON Formatter and its nine utilities are part of DevToolkit Pro, a one-time payment from $25 with no subscription.
Is my data sent to a server?
No. Formatting, decoding and hashing all run in your browser, which makes it safe for API responses and tokens.
Can it handle very large JSON files?
Yes. The tree view only builds the branches you open and groups long arrays into ranges, so documents with tens of thousands of records stay quick.
Does the JWT decoder verify signatures?
It decodes the header and payload and shows the expiry time. It does not verify the signature, which needs the secret or public key.
Why do large numbers look different in other JSON viewers?
Many viewers turn numbers into JavaScript numbers, which lose digits past 15 or so. This tree reads the original text, so every digit is kept.
Try JSON Formatter today
Install DevToolkit free, then unlock every Pro tool with one payment. No subscription.