Free online developer tools

214 tools

Small utilities developers reach for daily: JSON and YAML formatters, Base64 and URL encoders, regex testers, JWT decoders, diff viewers and cron helpers. Prefer tools marked as running in your browser when you paste tokens, keys or production data, because nothing is uploaded.

Showing 49–72 of 214

0.790score
DartPad
Dart team
Runs Dart and Flutter snippets in the browser with a console and a live preview pane.
ArtifactNo sign-up★ 1.9Kdeveloper tools
0.787score
Tiktokenizer
dqbd
Shows how OpenAI-style tokenizers split text or chat messages into tokens and counts them.
ArtifactNo sign-up★ 1.7Kdeveloper tools
0.786score
Are The Types Wrong?
Andrew Branch
Checks whether an npm package's TypeScript types resolve correctly across module systems.
ArtifactNo sign-up★ 1.6Kdeveloper tools
0.785score
Rust Playground
Rust project
Compiles and runs Rust code in the browser and shows output, assembly or MIR.
ArtifactNo sign-up★ 1.4Kdeveloper tools
0.784score
Random User Generator
RandomAPI
API and page that return random placeholder user profiles with names, photos and addresses.
ArtifactNo sign-up★ 1.5Kdeveloper tools
0.784score
Napkins.dev
Nutlope
Upload a wireframe or design screenshot and get a React and Tailwind app generated from it.
ArtifactAINo sign-up★ 1.5Kdeveloper tools
0.782score
TypeScript AST Viewer
David Sherret
Shows the TypeScript compiler's syntax tree and type info for code you paste.
ArtifactNo sign-up★ 1.4Kdeveloper tools
0.781score
publint
publint
Lints an npm package's package.json and exports so it works across bundlers and runtimes.
ArtifactNo sign-up★ 1.3Kdeveloper tools
0.780score
Wandbox
melpon
Compiles and runs C++ and other languages with many compiler versions and shareable permalinks.
ArtifactNo sign-up★ 1.3Kdeveloper tools
0.769score
bundlejs
okikio
Bundles, minifies and compresses npm packages in the browser to show gzip and brotli size.
ArtifactNo sign-upIn-browser★ 915developer tools
0.768score
Can I email
Rémi Parmentier
Lookup table showing which HTML and CSS features work in common email clients.
ArtifactNo sign-up★ 948developer tools
0.766score
Go Playground
Go team
Runs Go programs in a sandbox and shares them via link.
ArtifactNo sign-up★ 808developer tools
0.765score
GPT Tokenizer Playground
niieani
Visualises tokens for OpenAI models and estimates prompt cost against context limits.
ArtifactNo sign-up★ 857developer tools
0.765score
jq Playground
jq project
Runs jq filters on JSON in the browser and produces shareable links to the snippet.
ArtifactNo sign-up★ 856developer tools
0.764score
npmgraph
npmgraph
Draws the dependency tree of npm packages as an interactive graph with size and maintainer data.
ArtifactNo sign-up★ 799developer tools
0.764score
Raspberry Pi GPIO Pinout
Pinout.xyz
Interactive 40-pin GPIO reference with add-on boards and pin functions for the Raspberry Pi.
ArtifactNo sign-up★ 792developer tools
0.764score
Raspberry Pi Pico Pinout
Pinout.xyz
Interactive pin map of the Raspberry Pi Pico showing each pin's functions.
ArtifactNo sign-up★ 792developer tools
0.761score
ASN.1 JavaScript Decoder
Lapo Luchini
Parses DER, BER and PEM data such as certificates and keys into a readable ASN.1 tree.
ArtifactNo sign-upIn-browser★ 652developer tools
0.760score
CodeConverter
icsharpcode
Converts code between C# and VB.NET in both directions.
Artifact★ 916developer tools
0.755score
ESP Tool (esptool-js)
Espressif
Flashes firmware to ESP chips from the browser over Web Serial.
ArtifactNo sign-up★ 555developer tools
0.753score
tldr InBrowser
InBrowser.App
Offline-capable viewer of tldr-pages command cheat sheets that runs in the browser.
ArtifactNo sign-upIn-browser★ 466developer tools
0.751score
smee.io
Probot
Gives a public channel URL that forwards webhook payloads to your local machine.
ArtifactNo sign-up★ 485developer tools
0.747score
Embed Visualizer
leovoel
Live preview for Discord embed and webhook JSON so you can see how a message will render.
ArtifactNo sign-up★ 415developer tools
0.746score
Espruino Web IDE
Espruino
Writes JavaScript for Espruino boards and uploads it over Web Bluetooth or Web Serial.
ArtifactNo sign-up★ 386developer tools