Developer Tools
Format JSON, decode JWTs, generate UUIDs, test regex, convert between data formats, and build cron expressions. Every tool runs in your browser; no credentials or sensitive data leave your machine.
.gitignore Generator
Generate a .gitignore file by selecting technology presets — Node, Python, macOS, Windows, VS Code, and more. Deduplicates entries. Copy or download instantly.
Developer ToolsNew.htaccess Generator
Generate .htaccess rules for HTTPS redirect, GZIP, cache headers, security headers, and access control. Free, no upload.
Developer ToolsNewAES Encrypt / Decrypt
Encrypt and decrypt text with AES-256-GCM via the browser WebCrypto API. PBKDF2 key derivation. Nothing leaves your device — no upload, no server, no account.
Developer ToolsNewBarcode Generator
Generate Code 128 barcodes from any text in your browser. Download as PNG. No upload, no account, no logs.
Developer ToolsBase64 Encoder / Decoder
Encode text to Base64 or decode Base64 back to text. Runs entirely in your browser.
Developer ToolsNewBase64 Image Encoder
Convert any image to a Base64 data URL in your browser. Copy the string for HTML, CSS, or JSON. Free, no upload.
Developer ToolsNewBinary to Text Converter
Convert text to binary and binary to text. Supports ASCII encoding. Paste text or binary digits and get instant results.
Developer ToolsNewchmod Calculator
Convert Unix file permissions between numeric (755), symbolic (rwxr-xr-x), and human-readable forms. Browser-only, no upload.
Developer ToolsNewCode Formatter
Format and beautify JSON, CSS, HTML, and SQL code instantly. Free, in-browser, no upload.
Developer ToolsNewCode Line Counter
Count total, blank, comment, and code lines in pasted code. Supports 17 languages, runs entirely in your browser.
Developer ToolsColor Converter
Convert colors between HEX, RGB, and HSL. Instant, private, runs in your browser.
Developer ToolsNewContent Security Policy Builder
Build a Content Security Policy header by toggling directives and adding allowed domains. Outputs HTTP header and meta tag. Free, no upload.
Developer ToolsNewContext Packer
Pack prioritized prompt blocks into a context-window budget while reserving output tokens.
Developer ToolsNewContext Window Visualizer
See how your prompt fills different LLM context windows. Compare Claude, GPT-4o, Gemini across 9 models.
Developer ToolsNewCredit Card Number Validator
Validate credit card numbers using the Luhn algorithm. Identifies card type (Visa, Mastercard, Amex, etc.). No data leaves your browser.
Developer ToolsNewCron Expression Parser
Paste a cron expression and get a plain-English explanation plus the next 5 scheduled run times.
Developer ToolsNewCrontab Generator
Build and explain cron expressions field by field. Presets, live preview, plain-English description. Free, private.
Developer ToolsNewCSS / JS / HTML Minifier
Minify CSS, JavaScript, and HTML instantly in the browser. Strips comments and collapses whitespace to reduce file size. Free, private, no upload.
Developer ToolsNewCSS Border Radius Generator
Generate CSS border-radius with individual corner controls, live preview, and copy-ready output. Free, instant, no signup.
Developer ToolsNewCSS Box Shadow Generator
Generate CSS box-shadow with live preview. Control offset, blur, spread, colour, and opacity. Stack multiple layers. Copy ready-to-paste CSS instantly.
Developer ToolsNewCSS Flexbox Generator
Build CSS Flexbox layouts visually — toggle direction, wrap, justify-content, and alignment, then copy the generated CSS. Runs in your browser, no account required.
Developer ToolsNewCSS Gradient Generator
Create linear, radial, and conic CSS gradients with a live preview. Copy the CSS instantly. Free, runs in your browser.
Developer ToolsNewCSS Grid Generator
Build CSS Grid layouts visually — set columns, rows, gaps, and units, then copy the generated CSS. Runs in your browser, no account required.
Developer ToolsNewCSS Variables Generator
Build a CSS custom properties color palette — add named colors, set a variable prefix, and copy the ready-to-paste :root { --color-* } block. Free, instant, no signup.
Developer ToolsCSV to JSON
Convert CSV (or Excel/Sheets exports) to a JSON array of objects. Handles quoted fields. Free, private.
Developer ToolsNewcurl Command Builder
Build a curl command from a GUI — set method, headers, body, auth, and flags, then copy the result.
Developer ToolsNewDecimal ↔ Binary Converter
Convert numbers between decimal, binary, hexadecimal, and octal instantly. Enter any base and see all four representations at once. Free, instant, no signup.
Developer ToolsNewDockerfile Generator
Generate a production-ready Dockerfile for your language and runtime with best practices baked in.
Developer ToolsNewDomain Name Generator
Generate domain name ideas from your keywords across popular TLDs. Free, instant, private — runs in your browser.
Developer ToolsNewDownload Time Calculator
Estimate how long a file will take to download at a given internet speed. Supports Kbps, Mbps, and Gbps.
Developer ToolsNewEmail Address Validator
Validate email address format, detect common domain typos, and check MX record syntax. Instant, no email sent, fully private.
Developer ToolsNewEmail Signature Generator
Build a professional HTML email signature with name, title, company, contact links, and social icons — entirely in your browser.
Developer ToolsNewExcel to CSV
Convert Excel (.xlsx, .xls) or ODS spreadsheets to CSV in your browser. Select any sheet. Free, no upload.
Developer ToolsNewFake Data Generator
Generate rows of realistic test data — names, emails, addresses, UUIDs, and more. Export as CSV. Runs in your browser via @faker-js/faker, nothing is uploaded.
Developer ToolsNewFavicon Generator
Convert any image to favicon PNG files in all standard sizes (16px to 512px). Free, no upload.
Developer ToolsNewFew-Shot Prompt Builder
Build few-shot example collections for LLM prompts. Format for OpenAI, Claude, or plain text.
Developer ToolsNewFile Checksum Verifier
Compute SHA-256, SHA-512, or SHA-1 hash of any file in your browser. Verify against an expected checksum. No upload — your file never leaves your device.
Developer ToolsNewFile Size Converter
Convert file sizes between bytes, KB, MB, GB, TB, and PB in both decimal (÷1000) and binary (÷1024) modes. Free, instant, no signup.
Developer ToolsNewFine-Tune Cost Calculator
Estimate fine-tuning training tokens, training cost, and monthly inference cost from editable provider rates.
Developer ToolsNewGDPR Policy Analyzer
Paste a privacy policy to instantly check it against 15 GDPR requirements — data subject rights, DPO contact, retention, and more. Runs entirely in your browser.
Developer ToolsHash Generator
Generate SHA-256, SHA-512, SHA-1, and SHA-384 hashes from text. Runs in your browser.
Developer ToolsNewHeading Hierarchy Validator
Paste HTML or Markdown to validate h1–h6 heading nesting for accessibility and SEO. Free, instant, runs entirely in your browser.
Developer ToolsNewHTML Entity Encoder / Decoder
Encode special characters to HTML entities or decode entities back to text — instantly, in your browser.
Developer ToolsNewHTML to Markdown
Convert HTML to Markdown in your browser. Supports headings, lists, links, images, code blocks, and more. No upload, no account, no logs.
Developer ToolsNewHTTP Headers Decoder
Paste HTTP response headers to decode and understand each one. Covers security, caching, CORS and content headers.
Developer ToolsNewHTTP Status Code Reference
Free HTTP status code reference covering all 1xx–5xx codes with descriptions and developer tips. Search and filter instantly in your browser, no account required.
Developer ToolsNewIP Subnet Calculator
Calculate subnet mask, network address, broadcast address, and usable host range from an IP address and CIDR prefix.
Developer ToolsNewISBN Validator
Validate ISBN-10 and ISBN-13 numbers instantly in your browser — free, no account required. Detects the format and shows the normalized form.
Developer ToolsNewJavaScript Minifier
Minify JavaScript code by removing whitespace and comments. Instant, runs in your browser. No upload required.
Developer ToolsJSON Formatter
Format and validate JSON in your browser. Instantly pretty-print with 2 or 4 space indent.
Developer ToolsNewJSON Schema Generator
Paste any JSON and instantly generate a JSON Schema (draft-07). Free, instant, no upload.
Developer ToolsNewJSON to CSV
Convert a JSON array of objects to CSV (Excel/Sheets ready). Handles nested values and quoting. Free, private.
Developer ToolsNewJSON to TypeScript
Convert JSON objects to TypeScript interfaces instantly in your browser. Nested objects become nested interfaces. No upload, no account, no logs.
Developer ToolsNewJSON-LD Schema Builder
Generate JSON-LD structured data markup for Articles, Products, FAQ pages, and Local Businesses. Copy the ready-to-paste script tag for Google rich results.
Developer ToolsNewJSONL Formatter & Validator
Validate JSONL files line by line and convert between JSONL and JSON array. Free, in-browser.
Developer ToolsNewJSONPath Tester
Test JSONPath expressions against JSON data instantly. Supports dot notation and bracket notation. Results shown in real time.
Developer ToolsJWT Decoder
Decode and inspect JSON Web Token header and payload in your browser. No signature data leaves your device.
Developer ToolsNewJWT Generator
Generate signed JWT tokens with HS256, HS384, or HS512. Add custom claims, set expiry, copy the token. Free, in-browser.
Developer ToolsNewKanban Board
Simple online Kanban board with Todo, In Progress, and Done columns. Drag cards between columns.
Developer ToolsNewKeyboard Shortcut Reference
Searchable keyboard shortcut cheat sheet for VS Code, Chrome, macOS, Windows, Google Docs, Figma and Terminal.
Developer ToolsNewLLM Benchmark Comparison
Compare Claude, GPT-4o, Gemini, Llama and more on MMLU, HumanEval, MATH, GPQA and pricing. Sortable table.
Developer ToolsNewLLM Cost Calculator
Calculate and compare LLM API costs for Claude, GPT-4o, Gemini, Llama and more. Enter token counts to see exact pricing.
Developer ToolsNewLLM Error Decoder
Decode LLM API errors from OpenAI, Anthropic, Gemini, and Groq. Get causes and fixes instantly.
Developer ToolsNewLLM Eval Scorecard
Score LLM outputs manually across accuracy, completeness, instruction following, safety, and clarity.
Developer ToolsNewLLM Memory Calculator
Calculate how much VRAM you need to run any LLM. Covers fp32, fp16, int8, int4 quantization and KV cache.
Developer ToolsNewLLM Response Comparator
Compare two LLM outputs by tokens, words, shared terms, and lexical cosine similarity. No API key.
Developer ToolsNewllms.txt Generator
Generate an llms.txt file to guide AI crawlers — name, tagline, key resources, and opt-out flag.
Developer ToolsNewMeta Tag Generator
Generate SEO meta tags, Open Graph tags, and Twitter Card meta tags from a form — copy ready-to-paste HTML for your page's <head>.
Developer ToolsNewMIME Type Reference
Look up MIME types by file extension instantly. Free searchable reference covering 100+ types — images, documents, audio, video, fonts, and more. No account required.
Developer ToolsNewMorse Code Translator
Encode and decode Morse code instantly. Supports audio playback of dots and dashes. Free, runs in your browser.
Developer ToolsNewMy IP Address
Instantly see your public IP address, free and with no account required. One click to copy — your IP is never logged or stored.
Developer ToolsNewNginx Config Generator
Generate Nginx or Apache server block configs for static sites, reverse proxy, SSL redirect, or PHP-FPM. Free, browser-only.
Developer ToolsNumber Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal. Free, private, instant.
Developer ToolsNewOhm's Law Calculator
Calculate voltage, current, resistance, or power using Ohm's Law (V=IR). Enter any two known values to find the rest.
Developer ToolsNewOpen Graph Preview
Enter og:title, og:description, og:image, and og:url to preview how your share card looks on Twitter/X, LinkedIn, and Facebook — all in the browser.
Developer ToolsNewOpen Graph Tag Generator
Generate Open Graph meta tags for social media sharing with a live preview card showing how your page will look when shared on Facebook, LinkedIn, and other platforms.
Developer ToolsPassword Generator
Generate strong, random passwords in your browser. Customise length and character sets.
Developer ToolsNewPassword Strength Checker
Check how strong your password is with Shannon entropy calculation, crack time estimates, and NIST 800-63B security tips. Free, instant, runs entirely in your browser.
Developer ToolsNewPeriodic Table
Interactive periodic table with all 118 elements. Click any element for atomic data and electron configuration.
Developer ToolsNewPlaceholder Image Generator
Generate placeholder images of any size with custom background colour, text colour, and label. Free.
Developer ToolsNewPrime Number Generator
Generate all prime numbers in a given range using the Sieve of Eratosthenes. Runs entirely in your browser — no upload, no server.
Developer ToolsNewPrompt Compressor
Trim whitespace, comments, and filler phrases from prompts to reduce approximate token count before sending to an LLM.
Developer ToolsNewPrompt Formatter
Convert system and user messages into OpenAI, Claude, Gemini, or Llama API format. Copy-paste ready JSON.
Developer ToolsNewPrompt Injection Scanner
Scan user inputs for common prompt injection patterns before sending to your LLM. Free, in-browser.
Developer ToolsNewPrompt Library
Save, tag, search, and export your AI prompts locally — nothing leaves your browser.
Developer ToolsQR Code Generator
Generate a QR code from any text or URL and download it as PNG. Free, private, runs in your browser.
Developer ToolsNewRAG Chunk Previewer
Preview how your documents will be chunked for RAG (Retrieval-Augmented Generation). Adjust chunk size and overlap.
Developer ToolsNewRandom Number Generator
Generate cryptographically secure random integers or decimals. Set range, count, and unique-only — all in your browser.
Developer ToolsNewREADME Generator
Generate a professional README.md from a simple form — project name, description, features, installation, and licence. Copy the Markdown instantly. No account, no upload.
Developer ToolsRegex Tester
Test regular expressions against text. See all matches highlighted with position. Runs in your browser.
Developer ToolsNewResistor Color Code Calculator
Decode resistor color bands to find resistance value and tolerance. Supports 4-band and 5-band resistors. Instant, browser-based.
Developer ToolsNewRobots.txt Generator
Visual builder for robots.txt files. Add User-agent blocks, Allow/Disallow rules, and Sitemap URLs.
Developer ToolsNewSchema.org JSON-LD Generator
Generate valid Schema.org JSON-LD structured data for Article, Product, FAQ, HowTo, Event, and more — all in your browser.
Developer ToolsNewScreen Resolution Checker
Instantly check your screen resolution, viewport size, device pixel ratio, and color depth — free, in your browser, no account required.
Developer ToolsNewScreen Size Calculator
Calculate screen diagonal, PPI, and dimensions from width and height. Supports common aspect ratios like 16:9, 4:3, and 21:9.
Developer ToolsNewScript Generator
Generate Bash, PowerShell, Python or Node.js script scaffolds from a form. Includes arg parsing and logging.
Developer ToolsNewSEO Meta Preview
Preview how your page title and meta description appear in Google search results. Shows a live SERP snippet with character count indicators for both desktop and mobile views.
Developer ToolsNewSQL Formatter
Format and pretty-print SQL queries in your browser. Uppercase keywords, indent clauses, instant output. No upload, no account.
Developer ToolsNewSSH Key Generator
Generate RSA or EC SSH key pairs in your browser using the Web Crypto API. Keys never leave your device.
Developer ToolsNewSSH Key Generator
Generate RSA-4096 or Ed25519 SSH key pairs in your browser using WebCrypto. No upload, no server, fully private.
Developer ToolsNewString Escape Tool
Escape and unescape strings for JSON, HTML, SQL, Regex, and URL encoding. Free, runs in your browser.
Developer ToolsNewSubnet / CIDR Calculator
Calculate network address, broadcast, usable host range, and host count from any CIDR block — runs entirely in your browser.
Developer ToolsNewSystem Prompt Scorer
Score your LLM system prompt on 7 dimensions: role, task clarity, constraints, format, tone, context, and examples.
Developer ToolsNewText Similarity Checker
Compare two texts for lexical similarity using cosine similarity. Fast, in-browser, no API key.
Developer ToolsNewToken Counter
Count tokens, words, and characters in any text. See how your text fits in Claude, GPT-4o, or Gemini context windows.
Developer ToolsNewToken Probability Visualizer
Convert candidate token logits into softmax probabilities and see how temperature changes model sampling.
Developer ToolsNewTokenizer Visualizer
Visualize how your text is split into tokens for LLMs. See approximate token boundaries with color-coded highlights.
Developer ToolsNewTOML ↔ JSON Converter
Convert between TOML and JSON format bidirectionally in your browser. Supports nested objects, arrays, and all value types.
Developer ToolsNewTruth Table Generator
Enter a boolean expression (A, B, C, D with AND/OR/NOT/XOR) and generate the full truth table instantly.
Developer ToolsNewTwitter Card Generator
Generate Twitter Card meta tags with a live preview. Choose card type, add title, description, and image URL — get ready-to-paste HTML instantly.
Developer ToolsURL Encoder / Decoder
Encode special characters for URLs or decode percent-encoded strings. Instant, private.
Developer ToolsNewUsername Generator
Generate creative, memorable usernames from adjective-noun combinations. Choose your style, separator, and count. Runs in your browser — no account, no logs.
Developer ToolsUUID Generator
Generate cryptographically secure v4 UUIDs in your browser. Bulk generate up to 25 at once.
Developer ToolsNewViewport Inspector
See your current viewport width, height, device pixel ratio, and active Tailwind CSS breakpoint in real time.
Developer ToolsNewX.509 Certificate Decoder
Paste a PEM X.509 certificate to inspect subject, issuer, validity dates, SANs, and extensions — all in your browser.
Developer ToolsNewXML Formatter & Minifier
Format and pretty-print XML with custom indentation, or minify it to a single line — all in your browser.
Developer ToolsNewYAML ↔ JSON Converter
Convert YAML to JSON or JSON to YAML instantly in your browser. Supports nested structures, arrays, and custom indentation.
Developer ToolsNewYAML Formatter
Format and validate YAML instantly in your browser. Paste your YAML, get it pretty-printed and syntax-checked. No upload, no server.
Frequently Asked Questions
- Is it safe to paste API keys or credentials into these developer tools?
- Yes. All developer tools on brevio run client-side — your input is processed in JavaScript in your browser and never transmitted to a server. Verify with DevTools: open the Network tab and confirm no outbound requests fire when you paste input.
- Do these tools work with large files or long inputs?
- Yes, for practical development use cases. JSON formatters, diff checkers, and regex testers handle files up to several MB efficiently. Performance depends on your browser and device.
- Are the tools free with no limits?
- All developer tools are free with no usage limits, no rate limiting, and no signup required.
- Can I use these tools from the command line instead?
- Yes — most operations have CLI equivalents: jq for JSON formatting, openssl for hashing, git diff for text comparison, pandoc for Markdown conversion. The browser tools are faster for one-off use; CLI tools are better for scripted workflows.