Is my code or JWT sent to a server?

No. All processing is client-side. Your data never leaves your browser.

Can I use these tools offline?

Yes. Once loaded, all developer tools work without an internet connection.

Developer Tools

Daily-use developer utilities. Every tool runs in your browser — no API key, no rate limit, no telemetry on your code.

Sort:

.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

Barcode Generator

Generate Code 128 barcodes from any text in your browser. Download as PNG. No upload, no account, no tracking.

Developer Tools

Base64 Encoder / Decoder

Encode text to Base64 or decode Base64 back to text. Runs entirely in your browser.

Developer ToolsNew

Base64 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 ToolsNew

Code Formatter

Format and beautify JSON, CSS, HTML, and SQL code instantly. Free, in-browser, no upload.

Developer Tools

Color Converter

Convert colors between HEX, RGB, and HSL. Instant, private, runs in your browser.

Developer ToolsNew

Context Packer

Pack prioritized prompt blocks into a context-window budget while reserving output tokens.

Developer ToolsNew

Context Window Visualizer

See how your prompt fills different LLM context windows. Compare Claude, GPT-4o, Gemini across 9 models.

Developer ToolsNew

Crontab Generator

Build and explain cron expressions field by field. Presets, live preview, plain-English description. Free, private.

Developer ToolsNew

CSS 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 ToolsNew

CSS Gradient Generator

Create linear, radial, and conic CSS gradients with a live preview. Copy the CSS instantly. Free, runs in your browser.

Developer ToolsNew

CSS 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 Tools

CSV to JSON

Convert CSV (or Excel/Sheets exports) to a JSON array of objects. Handles quoted fields. Free, private.

Developer ToolsNew

Domain Name Generator

Generate domain name ideas from your keywords across popular TLDs. Free, instant, private — runs in your browser.

Developer ToolsNew

Fake 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 ToolsNew

Favicon Generator

Convert any image to favicon PNG files in all standard sizes (16px to 512px). Free, no upload.

Developer ToolsNew

Few-Shot Prompt Builder

Build few-shot example collections for LLM prompts. Format for OpenAI, Claude, or plain text.

Developer ToolsNew

File 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 ToolsNew

Fine-Tune Cost Calculator

Estimate fine-tuning training tokens, training cost, and monthly inference cost from editable provider rates.

Developer Tools

Hash Generator

Generate SHA-256, SHA-512, SHA-1, and SHA-384 hashes from text. Runs in your browser.

Developer ToolsNew

HTML Entity Encoder / Decoder

Encode special characters to HTML entities or decode entities back to text — instantly, in your browser.

Developer ToolsNew

HTML to Markdown

Convert HTML to Markdown in your browser. Supports headings, lists, links, images, code blocks, and more. No upload, no account, no tracking.

Developer ToolsNew

HTTP Headers Decoder

Paste HTTP response headers to decode and understand each one. Covers security, caching, CORS and content headers.

Developer Tools

JSON Formatter

Format and validate JSON in your browser. Instantly pretty-print with 2 or 4 space indent.

Developer ToolsNew

JSON Schema Generator

Paste any JSON and instantly generate a JSON Schema (draft-07). Free, instant, no upload.

Developer ToolsNew

JSON to CSV

Convert a JSON array of objects to CSV (Excel/Sheets ready). Handles nested values and quoting. Free, private.

Developer ToolsNew

JSON to TypeScript

Convert JSON objects to TypeScript interfaces instantly in your browser. Nested objects become nested interfaces. No upload, no account, no tracking.

Developer ToolsNew

JSONL Formatter & Validator

Validate JSONL files line by line and convert between JSONL and JSON array. Free, in-browser.

Developer Tools

JWT Decoder

Decode and inspect JSON Web Token header and payload in your browser. No signature data leaves your device.

Developer ToolsNew

JWT Generator

Generate signed JWT tokens with HS256, HS384, or HS512. Add custom claims, set expiry, copy the token. Free, in-browser.

Developer ToolsNew

LLM Benchmark Comparison

Compare Claude, GPT-4o, Gemini, Llama and more on MMLU, HumanEval, MATH, GPQA and pricing. Sortable table.

Developer ToolsNew

LLM Cost Calculator

Calculate and compare LLM API costs for Claude, GPT-4o, Gemini, Llama and more. Enter token counts to see exact pricing.

Developer ToolsNew

LLM Error Decoder

Decode LLM API errors from OpenAI, Anthropic, Gemini, and Groq. Get causes and fixes instantly.

Developer ToolsNew

LLM Eval Scorecard

Score LLM outputs manually across accuracy, completeness, instruction following, safety, and clarity.

Developer ToolsNew

LLM Memory Calculator

Calculate how much VRAM you need to run any LLM. Covers fp32, fp16, int8, int4 quantization and KV cache.

Developer ToolsNew

LLM Response Comparator

Compare two LLM outputs by tokens, words, shared terms, and lexical cosine similarity. No API key.

Developer Tools

Number Base Converter

Convert numbers between binary, octal, decimal, and hexadecimal. Free, private, instant.

Developer Tools

Password Generator

Generate strong, random passwords in your browser. Customise length and character sets.

Developer ToolsNew

Prompt Compressor

Trim whitespace, comments, and filler phrases from prompts to reduce approximate token count before sending to an LLM.

Developer ToolsNew

Prompt Formatter

Convert system and user messages into OpenAI, Claude, Gemini, or Llama API format. Copy-paste ready JSON.

Developer ToolsNew

Prompt Injection Scanner

Scan user inputs for common prompt injection patterns before sending to your LLM. Free, in-browser.

Developer Tools

QR Code Generator

Generate a QR code from any text or URL and download it as PNG. Free, private, runs in your browser.

Developer ToolsNew

RAG Chunk Previewer

Preview how your documents will be chunked for RAG (Retrieval-Augmented Generation). Adjust chunk size and overlap.

Developer ToolsNew

Random Number Generator

Generate cryptographically secure random integers or decimals. Set range, count, and unique-only — all in your browser.

Developer ToolsNew

README 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 Tools

Regex Tester

Test regular expressions against text. See all matches highlighted with position. Runs in your browser.

Developer ToolsNew

SQL Formatter

Format and pretty-print SQL queries in your browser. Uppercase keywords, indent clauses, instant output. No upload, no account.

Developer ToolsNew

String Escape Tool

Escape and unescape strings for JSON, HTML, SQL, Regex, and URL encoding. Free, runs in your browser.

Developer ToolsNew

System Prompt Scorer

Score your LLM system prompt on 7 dimensions: role, task clarity, constraints, format, tone, context, and examples.

Developer ToolsNew

Text Similarity Checker

Compare two texts for lexical similarity using cosine similarity. Fast, in-browser, no API key.

Developer ToolsNew

Token Counter

Count tokens, words, and characters in any text. See how your text fits in Claude, GPT-4o, or Gemini context windows.

Developer ToolsNew

Token Probability Visualizer

Convert candidate token logits into softmax probabilities and see how temperature changes model sampling.

Developer ToolsNew

Tokenizer Visualizer

Visualize how your text is split into tokens for LLMs. See approximate token boundaries with color-coded highlights.

Developer Tools

URL Encoder / Decoder

Encode special characters for URLs or decode percent-encoded strings. Instant, private.

Developer ToolsNew

Username Generator

Generate creative, memorable usernames from adjective-noun combinations. Choose your style, separator, and count. Runs in your browser — no account, no tracking.

Developer Tools

UUID Generator

Generate cryptographically secure v4 UUIDs in your browser. Bulk generate up to 25 at once.

Developer ToolsNew

XML Formatter & Minifier

Format and pretty-print XML with custom indentation, or minify it to a single line — all in your browser.

Developer ToolsNew

YAML ↔ JSON Converter

Convert YAML to JSON or JSON to YAML instantly in your browser. Supports nested structures, arrays, and custom indentation.

Frequently Asked Questions

Is my code or JWT sent to a server?: No. All processing is client-side. Your data never leaves your browser.
Can I use these tools offline?: Yes. Once loaded, all developer tools work without an internet connection.

More free toolsSee all 162 →

Merge PDFs Compress Image JSON Formatter Password Generator VAT Calculator QR Code Generator