Free Developer Tools — Format, Encode, Decode & Convert
A focused toolbox for everyday development work: format and validate JSON, encode and decode Base64 and URLs, decode and verify JWTs, test regular expressions, generate hashes and UUIDs, convert timestamps, and calculate subnets.
Every tool here runs entirely in your browser. That's not just a speed benefit — it means API responses, tokens, secrets and customer data you paste in are never transmitted anywhere. No signup, no rate limits, no waiting on a server round-trip.
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JSON Formatter & Validator
Pretty-print, minify and validate JSON with exact error line & column.
JSON Tree Viewer
Explore JSON as a collapsible tree.
JSON Diff / Compare
Compare two JSON documents and see what changed.
JSON to TypeScript
Generate TypeScript interfaces from JSON.
JSON ↔ CSV Converter
Convert JSON to CSV and CSV back to JSON.
JSON ↔ YAML Converter
Convert JSON to YAML and YAML back to JSON.
JSON ↔ XML Converter
Convert JSON to XML and XML back to JSON.
JSON Schema Generator
Generate a draft-07 JSON Schema from a sample.
JSONPath Tester
Query JSON with JSONPath expressions.
JSON Repair
Fix broken JSON — quotes, trailing commas, comments.
JSON Escape / Unescape
Escape text into a JSON string, or unescape it back.
64 Base644
Base64 Encode/Decode
Encode & decode Base64 with URL-safe, MIME and live modes.
File to Base64
Convert any file to Base64 or a data URI — in your browser.
Base64 to File
Decode Base64 (or a data URI) back into a downloadable file.
Image to Base64
Convert an image to a Base64 data URI with preview + CSS/HTML.
🔗 URL4
URL Encode/Decode
Percent-encode/decode with the right scope, live — plus double-encoding detection.
URL Parser
Break a URL into host, path, query params & hash.
Query String Builder
Build & edit query strings from key/value pairs.
Slugify — URL Slug Generator
Turn a title into a clean, SEO-friendly URL slug.
🔑 JWT3
More Developer tools
Regex Tester
Test regular expressions with live match highlighting.
Hash Generator
Generate SHA-1/256/384/512 hashes of text.
UUID Generator
Generate v4 UUIDs, single or in bulk.
Timestamp Converter
Convert between Unix epoch and human dates.
Case Converter
camelCase, snake_case, kebab-case, Title Case, and more.
CIDR / Subnet Calculator
Compute network, broadcast, mask, and host range.
What's included
- JSON — formatter and validator, tree viewer, diff, repair, schema generator, JSONPath tester, and converters to TypeScript, CSV, YAML and XML.
- JWT — decoder, encoder/signer and signature verifier using the Web Crypto API.
- Base64 — text, file, image and data-URI encoding and decoding.
- URL — percent encoder/decoder, URL parser, query-string builder and slug generator.
- Utilities — regex tester, hash generator, UUID generator, timestamp converter, case converter and CIDR calculator.
Why local processing matters for developers
Debugging usually means pasting real data — a production API response, an auth token, a config file. Pasting those into a tool that posts them to someone else's server is a quiet security problem, and one that's easy to overlook under time pressure. Because these tools compute in the browser, the data stays in the tab you're working in. You can use them on internal payloads without a second thought, and they keep working offline once the page has loaded.
Frequently asked questions
Is my data sent to a server?
No. Every developer tool here runs in your browser using JavaScript and the Web Crypto API, so what you paste never leaves your machine.
Can I use these on production data?
That's exactly the point of processing locally — nothing is transmitted or logged. As a general habit, still avoid pasting live production secrets into any web page, ours included.
Do the tools work offline?
Once a tool page has loaded, the processing itself needs no network connection, so it keeps working if you go offline.
Is there any rate limit or signup?
Neither. There's no account, no quota and no throttling, because there's no server doing the work.