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Clear explanations of core developer concepts. Read the theory, then try it in a hands-on tool.

JWT Explained

A JWT is a compact, URL-safe token for securely passing claims between parties. It consists of a Base64URL-encoded header, payload, and cryptographic signature. This guide explains what each part contains, how signing works, and the difference between HS256, RS256, and ES256.

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JWT VerifierJWT GeneratorJWT DecoderJWKS GeneratorRSA Key GeneratorECDSA Key Generator

HTTP Caching Guide

HTTP caching lets browsers and CDNs re-use responses without hitting the origin server. Cache-Control, Expires, ETag/If-None-Match, and Vary together form the caching contract. This guide explains each piece and when to use which strategy.

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Hash GeneratorTimestamp ConvertercURL ConverterSHA-256 GeneratorSHA-1 Generator

HTTP Redirect Guide

HTTP 301, 302, 303, 307, and 308 all redirect the browser, but they differ in permanence and whether the HTTP method (POST/GET) is preserved. This guide explains when each code applies, the link-equity impact on SEO, and common missteps.

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HTTP Status CodescURL Converter

Asymmetric Crypto Guide

Asymmetric cryptography uses a public/private key pair: one key to encrypt/sign, the other to decrypt/verify. RSA and ECDSA are the two major families used in JWTs, TLS, SSH, and WebAuthn. This guide compares their key sizes, speed, and use cases.

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RSA Key GeneratorECDSA Key GeneratorRSA Encrypt / DecryptJWT Generator

What is Base64

Base64 converts binary data (images, files, cryptographic keys) into 64 ASCII-safe characters — making it safe for email, JSON, URLs, and HTML data URIs. This guide explains encoding, decoding, variants (standard/URL-safe/MIME), and common pitfalls.

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Base64String to HexImage → Base64

What is a MIME Type

A MIME type (media type) tells browsers and HTTP clients how to interpret a file — whether to render it as HTML, parse it as JSON, display it as a PNG, or download it. This guide covers the Content-Type header, common types, and the pitfalls that break rendering.

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SVG OptimizerJSON Formatter

How Hex Encoding Works

Hexadecimal (hex) turns every byte into 2 readable characters — A→41, 中→e4b8ad, 😀→f09f9880. Learn how string-to-hex conversion works under the hood, why developers use it for debugging, crypto hashes, and memory dumps.

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String to HexHex to StringBinary to HexBase64SHA-256 Generator

How Content-Disposition Works

The Content-Disposition HTTP header controls whether a file downloads or opens inline, and specifies the filename to save. Learn how attachment, inline, and filename* (RFC 5987) work, and why non-ASCII filenames break in older browsers.

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URL Encode/DecodePunycode

How SHA-256 Works

SHA-256 produces a fixed 256-bit fingerprint for any input, from a single word to a 10 GB file. It's the hash behind TLS certificates, Bitcoin mining, and Git object-IDs. Learn how it works at a conceptual level and why collision resistance matters.

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SHA-256 GeneratorSHA-512 GeneratorSHA-1 GeneratorHash GeneratorHMAC Generator

HTTP 4xx Client Errors

HTTP 4xx status codes mean 'the client sent something wrong.' 400 Bad Request, 403 Forbidden, 404 Not Found, 413 Payload Too Large, and 414 URI Too Long are the most common. This guide explains what triggers each, and what to check first.

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HTTP Status CodescURL ConverterURL Encode/DecodeURL Parser

How CSS Gradients Work

CSS gradients generate smooth color transitions without any image files. Learn how linear-gradient, radial-gradient, and conic-gradient syntax works — angles, color stops, hard stops, repeating patterns, and Tailwind equivalents.

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CSS GradientBox ShadowGlassmorphismBorder Radius

How Duplicate Detection Works

Learn how duplicate-finding works — case-insensitive matching, whitespace trimming, frequency counting, and the difference between finding duplicates vs removing them. Covers the common real-world scenarios where duplicates cause data bugs.

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Duplicate FinderRemove DuplicatesLine CounterText Sort

How to Convert CSV to JSON

Learn how to convert CSV (comma-separated values) to JSON in the browser, Python, Node.js, and Go. Covers header-mapping, nested-object flattening, and handling CSV quirks like embedded commas and quotes.

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CSV → JSONJSON → CSVJSON FlattenJSON Formatter

How to Compress Images

Learn how image compression works — lossy vs lossless, how JPG/PNG/WebP compression differs, what quality setting to choose, and how to batch-compress images without losing visible quality.

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Image CompressorImage ResizerImage → WebPImage → AVIFImage Cropper

How to Merge PDFs

Learn how to merge multiple PDFs into a single document — online, free, and without uploading files. Covers page ordering, selective page ranges, and why client-side PDF tools are safer than upload-based services.

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Merge PDFSplit PDFRemove PDF PagesPDF Text ExtractorPDF Password Remover

How to Create a QR Code

Learn how to generate QR codes for URLs, text, WiFi credentials, vCard contacts, and more — with custom colors, error correction, and logo embedding. Everything runs client-side, no server needed.

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QR CodeQR ReaderBase64URL Encode/Decode

How to Extract Text from PDF

Learn how to extract plain text from PDF files — online, free, no upload. Covers the types of PDF (text-based vs scanned/image-based), why copy-paste fails on some PDFs, and how to automate extraction for hundreds of documents.

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PDF Text ExtractorMerge PDFSplit PDFPDF Password RemoverPDF → Images

How to Convert JSON to Excel

Learn how to convert JSON arrays to CSV/Excel spreadsheets — flatten nested objects, pick columns to keep, handle date formatting, and download CSV files that open correctly in Excel and Google Sheets.

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JSON → CSVCSV → JSONJSON FlattenJSON FormatterJSON Path Finder

HTTP Expires Header Explained

The Expires response header tells browsers and CDNs a wall-clock deadline after which a resource is stale. Learn the exact HTTP-date format, four production-ready configurations (Apache, Nginx, Express, CDN), how Expires interacts with Cache-Control, and why max-age replaced it as the preferred caching directive.

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URL ParserTimestamp Converter

Encoding vs Encryption

Encoding and encryption both transform data, but they serve completely different purposes. Encoding (Base64, Hex, URL encode) is a reversible representation with no security — anyone can decode it. Encryption (AES, RSA) requires a key and is designed to keep data secret from unauthorised parties. Learn the key differences and which one to use for your use case.

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Base64URL Encode/DecodeHex to StringAES Encrypt / DecryptRSA Key GeneratorJWT Decoder