Free Online Developer Tools
Fast, private, and reliable browser-based utilities for developers. No data leaves your device β everything runs 100% client-side.
Why Choose DevHelper Tools?
Privacy First
All tools run entirely in your browser. Your data is never sent to any server, ensuring complete privacy and security.
Lightning Fast
No server round-trips. Instant results powered by modern browser APIs. Works offline after the first load.
Always Free
All tools are completely free to use with no sign-up required. No usage limits, no paywalls.
Multi-Language
Available in 6 languages including English, Chinese, Japanese, Spanish, French, and German.
High-retention developer workflows
The homepage now highlights sticky developer workflows: reverse-generate cron rules, inspect regex backtracking risk, audit JWTs, generate Docker stacks, compare structured data, and fix i18n gaps without leaving the browser.
Cron Expression Debugger
Explain cron expressions in both directions, predict upcoming runs, and debug scheduler rules safely in the browser.
Write a schedule in natural language, generate a cron expression, then preview the next ten execution times in your local timezone.
Regex Tester
Test regex patterns, inspect a token-by-token flow view, and spot likely backtracking or ReDoS risks before they hit production.
Trace a regex token-by-token, inspect likely backtracking hotspots, and verify real matches before it lands in production validation.
JWT Decoder & Security Auditor
Decode and inspect JSON Web Tokens with client-side security checks for none algorithm, expiry, audience, issuer, and risky claim setups.
Decode tokens and surface dangerous choices like none algorithm, missing exp, long-lived claims, or issuer/audience gaps.
Dockerfile / Compose Generator
Generate production-minded Dockerfile and docker-compose templates with multi-stage builds, non-root runtime users, and optional Prisma/Postgres/Redis blocks.
Generate production-minded Dockerfile and docker-compose templates with multi-stage builds, non-root runtime users, and optional Prisma/Postgres/Redis blocks.
Structured Data Diff
Compare JSON, YAML, and XML by normalizing them into a single structure and highlighting field-level differences.
Compare JSON, YAML, and XML by normalizing them into a single structure and highlighting field-level differences.
i18n Missing Key Detector
Compare locale JSON files, find missing keys, and flag interpolation parameter mismatches before they ship to users.
Compare locale JSON files, find missing keys, and flag interpolation parameter mismatches before they ship to users.
Available Tools
Encoding
Base64 Encoder / Decoder
Encode and decode text or files using Base64 encoding
URL Encoder / Decoder
Encode and decode URL components and full URLs
Unicode Converter
Convert text to Unicode code points and vice versa
JSON Escape / Unescape
Escape and unescape strings for use in JSON
Morse Code Converter
Encode text into Morse code or decode Morse code back to text. Supports International Morse (ITU) including letters, digits, and punctuation.
JWT Decoder & Security Auditor
Decode and inspect JSON Web Tokens with client-side security checks for none algorithm, expiry, audience, issuer, and risky claim setups.
Crypto
Time
Format
JSON Formatter / Validator
Format, minify and validate JSON data
SQL Formatter
Format and beautify SQL queries
XML Formatter
Format, minify and validate XML documents
YAML β Properties Converter
Convert between YAML and Java .properties format
Structured Data Diff
Compare JSON, YAML, and XML by normalizing them into a single structure and highlighting field-level differences.
Dev
Regex Tester
Test regex patterns, inspect a token-by-token flow view, and spot likely backtracking or ReDoS risks before they hit production.
Nginx Config Generator
Generate nginx configuration files by selecting options. Supports SSL, reverse proxy, caching, security headers, and more.
UUID / ULID Generator
Generate UUIDs (v1, v4, v7) and ULIDs in bulk. UUID v7 is timestamp-prefixed and lexically sortable β great for database keys.
Number to Chinese Capital
Convert numbers to formal Chinese capital characters (ε£Ήθ΄°ε) used on invoices, contracts, and financial documents. Also produces simple (lowercase) Chinese.
Dockerfile / Compose Generator
Generate production-minded Dockerfile and docker-compose templates with multi-stage builds, non-root runtime users, and optional Prisma/Postgres/Redis blocks.
Mock Data Generator
Turn JSON samples into realistic mock data arrays with smart field inference for email, avatar, ids, totals, timestamps, and more.
cURL / Fetch / Axios Converter
Parse cURL commands into structured requests and convert them to Fetch, Axios, or Python requests code.
i18n Missing Key Detector
Compare locale JSON files, find missing keys, and flag interpolation parameter mismatches before they ship to users.
Coredump Analyzer
Upload a core dump for browser-side heuristic analysis: file format, crash signals, likely fault classes, and triage hints before you open gdb.
Heapdump Analyzer
Inspect Node / V8 heap snapshots in the browser, summarize node counts, dominant object types, and first-pass memory leak hints.
Visual
QR Code Generator
Generate and scan QR codes instantly
Graphviz Viewer
Render Graphviz DOT language diagrams as SVG
Color Converter & Picker
Convert colors between HEX, RGB, HSL, HSV, and CMYK formats. Includes a color picker and shade preview.
CSS Layout Sandbox
Prototype Grid and Flexbox layouts visually, tweak item spans, and export responsive HTML/CSS snippets.
SVG Optimizer & Path Extractor
Clean raw SVG markup, inspect path data, and generate React/Vue icon component boilerplate plus path animation CSS.
Latest guides
QR Codes, Properly Explained
How QR codes actually work β finder patterns, Reed-Solomon error correction, static vs. dynamic redirects, and the real reasons codes fail in print.
Base64, Properly Explained
A 1989 hack for smuggling binary through 7-bit email transports β and why we still use it for JWTs, data URIs, and a hundred other places. Two alphabets, one common decode failure, and the things it categorically isn't.
URL Encoding, Properly Explained
Why %20 and + both mean space, why encodeURI and encodeURIComponent are not interchangeable, and how the HTML form spec quietly invented its own incompatible variant. RFC 3986 vs application/x-www-form-urlencoded.
Frequently Asked Questions
Is it safe to use these tools with sensitive data?
Yes! All processing happens locally in your browser. Your data never leaves your device. We do not collect, store, or transmit any data you enter into our tools.
Do I need to create an account?
No. All tools are freely available without registration. Simply open the tool you need and start using it immediately.
Do the tools work offline?
Yes. Once the page is loaded, all tools work without an internet connection since they run entirely in your browser.
What browsers are supported?
DevHelper Tools works on all modern browsers including Chrome, Firefox, Safari, and Edge. We recommend using the latest version for the best experience.
How is this different from other online dev tools?
Unlike most online tools that send your data to a server for processing, our tools run 100% client-side. This means your sensitive data (passwords, API keys, private code) stays on your machine.