developer tools
100% offline
No uploads
Free · no signup
22 tools
Developer tools
Offline developer tools are browser-only utilities for formatting, decoding, parsing, and inspecting the kinds of data developers paste into a tab every day — JSON, JWTs, regex, hashes, UUIDs, cron expressions — with no server round-trip and no risk of leaking production payloads to a third party.
Every Developer tool
- JSON FormatterFormat, validate and minify JSON entirely in your browser.
- Base64 Encoder / DecoderEncode text to Base64 and decode it back, all offline.
- Base32 Encoder / DecoderEncode and decode Base32 — RFC 4648, extended hex, Crockford and z-base-32.
- Base58 Encoder / DecoderEncode, decode and checksum-verify Base58 and Base58Check.
- Base85 Encoder / DecoderAscii85 and Z85 encoding — denser than Base64, with strict validation.
- URL Encoder / DecoderPercent-encode and decode URL components instantly.
- URL ParserBreak any URL into its protocol, host, path and query parameters.
- JWT DecoderDecode and inspect JSON Web Token claims without sending them anywhere.
- Regex TesterTest JavaScript regular expressions with live match highlighting.
- UUID GeneratorGenerate cryptographically random UUIDs (v4) in bulk.
- ULID GeneratorGenerate time-ordered, URL-safe ULIDs in bulk.
- Hash GeneratorCompute SHA-256, SHA-1, SHA-512 and MD5 hashes in the browser.
- Timestamp ConverterConvert Unix time in any unit — seconds to nanoseconds — with exact precision.
- Subnet CalculatorCIDR and subnet maths for IPv4 and IPv6 — split, plan VLSM, summarise.
- Cron Expression ExplainerTranslate cron expressions into plain English and preview the next runs.
- CSS Flexbox & Grid PlaygroundVisually compose Flexbox and Grid layouts and copy the CSS.
- Number Base ConverterConvert numbers between binary, octal, decimal, hex and any base.
- SQL FormatterBeautify and standardize SQL queries for 7 dialects, in your browser.
- HTML FormatterBeautify minified HTML with Prettier, including inline CSS and JS.
- CSS FormatterBeautify minified CSS, SCSS and Less with Prettier, in your browser.
- JavaScript FormatterBeautify minified JS, JSX, TypeScript and TSX with Prettier.
- HTML Entity Encoder / DecoderEncode text to HTML entities and decode them back.
About developer tools
Every developer tool on offlineutils.com runs entirely in your browser using native Web APIs (JSON.parse, crypto.subtle, RegExp, URL). That matters because the data you paste into these tools is often sensitive: production API responses, JWT bearer tokens, internal config files, customer payloads. Web-based formatters that upload your data to a server have a long history of accidental leaks. The tools here are auditable — open DevTools → Network, click any button, and watch zero requests fire.
Why pick offline developer tools
- Zero uploads — data never leaves your browser
- No cookies, ads, fingerprinting, or cross-site tracking
- Free, no signup or account required
- Works offline once loaded; installable as a PWA
- Verifiable in DevTools — zero network calls when you press a button
Frequently asked questions
Are these developer tools really offline?
Yes. Every tool runs entirely in your browser using native Web APIs. After you load a tool page once, you can open it again with the network disconnected and it still works. Open DevTools → Network and confirm zero requests when you press a button.
Why use a browser tool instead of a CLI like jq or openssl?
Two reasons. First, you do not need to install or remember syntax — paste and read. Second, you can use these on any machine (a borrowed laptop, a phone, a locked-down corporate device) where installing tooling is not an option. CLIs are still better for scripting and pipelines.
Are these tools safe for production secrets?
Yes, because nothing is uploaded. JWTs are decoded in-browser, hashes are computed via crypto.subtle locally, JSON is parsed by the native JSON.parse. The single thing to be careful about is that any text you paste is visible to whoever can see your screen and to any browser extensions that read page content — the same as any browser tab.
Do these tools work on mobile?
Yes. Every tool here is responsive and works in any modern mobile browser. Install offlineutils.com as a PWA to keep them available without an internet connection.