Is my input uploaded to a server?

Most tools run entirely in your browser and never upload your input. The few features that need the network say so on the page. Anonymous usage analytics are described in the Privacy Policy.

Do I need an account or to pay?

No. All tools are free and require no sign-up.

How do I suggest a tool or report a bug?

Use the Contact page to send ideas or issues; we keep adding and improving tools based on feedback.

How do I switch between English and Chinese?

Use the language switcher at the top of the page. English pages live under /en, e.g. devtool.tech/en/about.

About Developer's Arsenal - Free Local Tools

About Developer's Arsenal

A free, local-first, bilingual toolbox for developers.

Developer's Arsenal (devtool.tech) brings together 60+ small tools you reach for every day: encoding, JWT, color, tables, images, Markdown and more. Open a page and use it — no sign-up, and most tools process data right in your browser. Think of it as a handy Swiss Army knife for the tedious little tasks you can't avoid.

What it helps you do

Debug JWTs during API integration
Got a token and need to see the user claims and expiry? Decode it, turn exp / iat into readable dates, or sign a test token yourself.
JWT Decoder →JWT Encoder →Timestamp Converter →
Convert between CSV, Excel and Markdown tables
Paste an exported CSV and get a Markdown table for your docs or PR description in one click; JSON, SQL, HTML and more are supported too.
Table Converter →CSV to Markdown →
Work with colors, contrast and accessibility
Convert between HEX, RGB, HSL and OKLCH, check text/background contrast against WCAG, and simulate how color-blind users see your design.
Color Converter →Contrast Checker →Color Blindness Simulator →
Compress and prep images before shipping
Batch-compress images to cut file size, or remove backgrounds to get a transparent image — all processed locally.
Image Compressor →Background Remover →

Tool map

Browse every tool by topic; each topic page has featured tools and an FAQ.

Tool Topics

Markdown Tools

HTML to Markdown, directory trees, table conversion, and batch URL processing.

Encoding & Hashing

Base64, URL encoding, hash generation, and UTF-8 charset conversion.

JWT Debugging

Decode and encode tokens, and check timestamps.

Color Tools

Convert colors, check contrast, build palettes, and explore OKLCH.

Table Tools

Convert and generate CSV, JSON, Markdown, HTML, Excel, and more.

Image Tools

Compress, remove backgrounds, watermark, read EXIF, and convert formats.

Developer Tools

UUIDs, timestamps, passwords, hashes, ASCII codes, and IP lookup.

Our principles

Local-first: Anything that can run in the browser stays there — tokens, tables and images you paste are not uploaded by default.
No sign-up, no paywall: Every tool is free, needs no account, and never asks you to pay halfway through.
English and Chinese: UI and docs are available in both languages, with keyboard and screen-reader use in mind.
Transparent analytics: We use cookies to store preferences such as language, and may use analytics tools such as Google Analytics to collect anonymous usage data to improve the product.

For details on data and cookies, see our Privacy Policy

About the author

Developer's Arsenal is built and maintained independently by Shanyue, who writes about frontend and engineering. Read more on his blog: shanyue.tech

FAQ

Is my input uploaded to a server?: Most tools run entirely in your browser and never upload your input. The few features that need the network say so on the page. Anonymous usage analytics are described in the Privacy Policy.
Do I need an account or to pay?: No. All tools are free and require no sign-up.
How do I suggest a tool or report a bug?: Use the Contact page to send ideas or issues; we keep adding and improving tools based on feedback.
How do I switch between English and Chinese?: Use the language switcher at the top of the page. English pages live under /en, e.g. devtool.tech/en/about.

About