DevTools Pro - Developer Toolbox

A developer toolbox that formats, converts, compares and inspects text and API data locally. Zero permissions, no account.

DevTools Pro is a free developer toolbox with 14 tools in one popup — JSON, API requests, encoding, timestamps, large-file extraction and more. Zero permissions. Every tool opens in the toolbar popup; one click (⤢) expands it into its own floating window, so you can keep working without another browser tab. ━━━━━━━━━━━━━━━━━━━━ 🧰 TOOLS INCLUDED 1. JSON Formatter • Collapsible tree view with per-level indentation guides • Live validation: errors are underlined in the editor with line/column and a plain-language reason • Tolerant repair fixes unquoted values, missing commas and unclosed brackets — and says what it changed • Pasting an object or array formats it and renders the tree automatically • Deep search across keys and values, jumping to the N-th match • Copy any subtree as JSON, or minify to one line • Large files render progressively; Ctrl+Z / Ctrl+Y keep the tree in sync • Bracket/quote auto-closing and Tab indentation 2. API Client • Send HTTP/HTTPS requests: method, URL, query params, headers, body • Body types: JSON, text, x-www-form-urlencoded, form-data • Response views: Pretty / Raw / collapsible tree / headers, with status, timing and size • Up to 8 request tabs, each keeping its own draft, response and sub-tab • Tabs, drafts and the last 50 requests are stored in this extension's own IndexedDB; response bodies and credential-looking values are not written • Pre-send checks flag what the browser will silently change (forbidden headers, duplicate keys, GET with a body) • CORS-aware: a blocked cross-origin request gets a diagnosis instead of a bare “Failed to fetch”, plus “open GET in a new tab” as a fallback 3. Format Converter (JSON ↔ YAML ↔ CSV) • Four-way conversion between JSON, YAML and CSV • YAML subset (mappings, lists, scalars) parsed without a third-party library • CSV follows RFC 4180, with type inference for numbers and booleans 4. Text Diff • Line-by-line LCS with prefix/suffix pruning, so large inputs stay usable • Word-level highlighting inside changed lines, ±3 lines of context • Click a result line to jump back to the matching line in Original or Changed and select it 5. Mock Data • Names, emails, phone numbers, UUIDs, IPs, URLs, user agents, test card numbers, dates, companies, addresses, passwords • Output as JSON, plain lines or CSV 6. Base64 Encode / Decode • UTF-8 safe — Chinese and emoji survive the round trip • Bidirectional, one click each way 7. URL Encode / Decode • Standard encodeURIComponent / decodeURIComponent • One-click copy 8. Regex Tester • 20-pattern library plus snippet insertion • Token-by-token explanation of what the expression does • Real-time match highlighting and count; g / i / m toggles • Invalid patterns show the error under the pattern instead of a silent empty result 9. JWT Encode / Decode • Decode: header, payload and signature split, with expiry check • Encode: HS256/384/512 signing via Web Crypto • 4 payload templates (Basic, Auth, Admin, API) • Custom expiry: minutes, hours, days or a specific date 10. Timestamp Converter • One input accepts Unix seconds, milliseconds, a date-time string or ISO 8601 • Local time as the headline (weekday + relative time), then UTC / ISO 8601 / Unix seconds / milliseconds • 9 time zones, click a row to copy • “Now”, “today 00:00”, “this time yesterday”, “in a week” shortcuts 11. HTTP Reference • 61 status codes and 36 MIME types • Live filter; click a row to copy 12. Cron Parser • 5-field expressions, plus 6-field (with seconds) and @daily / @weekly macros • Next runs and a plain-language explanation of the schedule • Supports */n steps, a-b ranges and MON-FRI / JAN style aliases • Warns about schedules that never fire (such as Feb 30) and out-of-range steps 13. Color Tools • HEX / RGB / HSL conversion with two editable swatches • WCAG contrast ratio (AA 4.5 / large text 3 / AAA 7) • Live sample card: your foreground on your background 14. Big Text (large-file line extraction) • Open a UTF-8 text file up to 50 MB and declare a range by line number, text marker or regex — a clickable counterpart to sed -n '/A/,/B/p' • Both endpoints are included; every pair of the same markers is enumerated and switchable with ‹ › • Virtualized full-file preview: only the visible rows are rendered, long lines scroll horizontally, line numbers stay pinned on the left • Click a line number to set the start, Shift-click for the end; Ctrl/⌘-drag in the text to select a range, then copy it or export .txt • Native text selection works too (rows tint, copied text excludes line numbers) • Find (Ctrl+F) in fuzzy / exact / multi-word modes; jumping scrolls horizontally to the word and opens the full-line overlay when the hit falls in a truncated long line • Double-click a line over 20,000 characters to read it in a chunked overlay; the file is never modified, uploaded or written back ━━━━━━━━━━━━━━━━━━━━ 🔒 PRIVACY FIRST • Zero permissions — no permissions, no host access, no content scripts • No analytics, no tracking, no ads, no account • Data stays on your device: tabs, drafts and history live in this extension's own IndexedDB (no storage permission, no sync, no server of ours); the home screen only remembers tool ids and timestamps for its “recent” row. Export everything as JSON, import on another machine, or erase it from Settings • Credential-looking header values (Authorization, Cookie, *token*, *secret*, *password*) are not written to disk by default • The API Client sends a request only when you click Send, directly from your browser to the address you typed. There is no server of ours in between — we cannot see, store or relay your requests • Big Text files are read into memory only: never uploaded, never written back, never saved to the extension database • Because no host permissions are requested, cross-origin API responses follow the browser's normal CORS rules: a response can be read only if the target server allows it • Open privacy policy linked below 🌐 INTERNATIONAL • Full English & Simplified Chinese support • Auto-detects browser language 💡 PERFECT FOR • Frontend/backend developers debugging APIs • QA engineers inspecting JWT tokens and diffing payloads • DevOps engineers converting timestamps and reading Cron schedules • Anyone working with large logs, JSON, YAML, CSV or encoded data ──────────────────────────── 📬 Support: 13531021638@163.com