# ZeroUtil

> Free online browser-based utility tools for developers and everyday users.
> 230+ tools run entirely in your browser - no signup, no install required.

## Tools

- [QR Code Generator](https://zeroutil.com/tools/qr-code-generator/) : Generate QR codes for URLs, text, email, phone and WiFi.
- [QR Code Reader](https://zeroutil.com/tools/qr-code-reader/) : Scan and decode QR codes from any image online - upload a photo, screenshot or saved picture and read the QR contents instantly in your browser.
- [Fraction Calculator](https://zeroutil.com/tools/fraction-calculator/) : Add, subtract, multiply and divide fractions with simplified results.
- [Base64 Encoder & Decoder](https://zeroutil.com/tools/base64-encode-decode/) : Encode UTF-8 text to Base64 online or decode Base64 back to UTF-8 and plain text. Runs in your browser with no upload.
- [Readability Checker](https://zeroutil.com/tools/readability-score/) : Free reading level checker and writing grade level analyzer. Flesch-Kincaid, Flesch Reading Ease, Gunning Fog and Coleman-Liau scores in one place.
- [Percentage Calculator](https://zeroutil.com/tools/percentage-calculator/) : Calculate percentages: X% of Y, percentage increase/decrease, and more.
- [ROI Calculator (Return on Investment)](https://zeroutil.com/tools/investment-return-calculator/) : Calculate ROI, CAGR, annual return and percentage gain from initial investment, final value and holding period. Works for stock ROI, after-tax ROI, social ROI and required-return scenarios.
- [Energy Converter](https://zeroutil.com/tools/energy-converter/) : Convert between joules, calories, kilocalories, BTU, kilowatt-hours and electronvolts.
- [PDF Password Protect](https://zeroutil.com/tools/pdf-password-protect/) : Add AES-256 password protection to PDF files via qpdf. Files auto-deleted after 15 minutes.
- [Audio Waveform Generator](https://zeroutil.com/tools/audio-waveform-generator/) : Generate a SoundCloud-style waveform image from any audio file. Decoded in your browser, exported as PNG or SVG.
- [Discount Calculator](https://zeroutil.com/tools/discount-calculator/) : Calculate discount amount, sale price, savings, and discounted value with optional sales tax. Supports stacked coupons.
- [Tax Bracket Calculator](https://zeroutil.com/tools/tax-bracket-calculator/) : Calculate federal income tax using 2024 and 2025 US tax brackets, with 2023 reference. See effective rate, marginal rate and tax per bracket.
- [Image Cropper](https://zeroutil.com/tools/image-cropper/) : Crop images with preset aspect ratios like 1:1, 16:9, and 4:3 using a visual editor.
- [Sleep Cycle Calculator](https://zeroutil.com/tools/sleep-calculator/) : Find when to sleep or wake up based on 90-minute REM cycles. Free bedtime and wake time calculator.
- [Color Palette Generator](https://zeroutil.com/tools/color-palette-generator/) : Generate harmonious color palettes, Tailwind-style 50-900 scales and design-system tokens from any base hex color. Also a hex color palette generator (Farbpalette Generator auf Deutsch).
- [Unicode Text Converter](https://zeroutil.com/tools/unicode-text-converter/) : Convert text to bold, italic, script, fraktur and other Unicode styles.
- [Base64 to Image Converter](https://zeroutil.com/tools/base64-to-image/) : Decode a Base64 string or data URL back into a viewable image and download it as PNG, JPG, WebP or GIF. Runs in your browser.
- [Tile Calculator](https://zeroutil.com/tools/tile-calculator/) : Calculate tiles needed for floors or walls with grout spacing and waste percentage.
- [Unix Timestamp Converter](https://zeroutil.com/tools/unix-timestamp-converter/) : Convert Unix timestamps to human-readable dates and back.
- [Secure Token Generator](https://zeroutil.com/tools/secure-token-generator/) : Generate cryptographically secure random tokens in base64url, hex, alphanumeric or UUID v4 format.
- [Word Counter](https://zeroutil.com/tools/word-counter/) : Count words, characters, sentences, paragraphs and estimate reading time.
- [XML Sitemap Generator](https://zeroutil.com/tools/xml-sitemap-generator/) : Generate valid XML sitemaps from a list of URLs with changefreq and priority.
- [Video Compressor](https://zeroutil.com/tools/video-compressor/) : Compress MP4, WebM and MOV videos with H.264 to make them smaller for sharing. Files auto-deleted after 15 minutes.
- [URL Encoder / Decoder](https://zeroutil.com/tools/url-encode-decode/) : Online URL encoder and decoder for query strings, paths, and HTTP request values - percent-encodes characters with encodeURIComponent.
- [Basic Auth Header Generator](https://zeroutil.com/tools/basic-auth-header-generator/) : Create HTTP Basic Authentication headers from a username and password or API token.
- [CSS Box Shadow Generator](https://zeroutil.com/tools/box-shadow-generator/) : Create CSS box shadows with a visual editor. CSS box-shadow generator, shadow maker and box-shadow builder with live preview, multi-layer support and Material elevation presets.
- [Salary to Hourly Converter](https://zeroutil.com/tools/salary-to-hourly-converter/) : Convert an annual salary to an hourly wage and back. Hourly, weekly, bi-weekly, monthly and annual figures side by side.
- [Markdown Table Generator](https://zeroutil.com/tools/markdown-table-generator/) : Build a Markdown table interactively. Add rows and columns, set per-column alignment and copy the GitHub-flavoured output.
- [Robots.txt Generator](https://zeroutil.com/tools/robots-txt-generator/) : Generate robots.txt files with user-agent rules, allow/disallow paths and sitemap.
- [Water Intake Calculator](https://zeroutil.com/tools/water-intake-calculator/) : Calculate daily water intake based on body weight, activity level and climate.
- [SEO Word Counter](https://zeroutil.com/tools/seo-word-counter/) : Count words, characters, headings, paragraphs with keyword density and reading level.
- [Lorem Ipsum Generator](https://zeroutil.com/tools/lorem-ipsum-generator/) : Generate placeholder text in paragraphs, sentences or words.
- [AES-256 Encrypt / Decrypt Online - Free, In-Browser](https://zeroutil.com/tools/aes-encrypt-decrypt/) : Encrypt and decrypt text with AES-128, AES-192, or AES-256 in GCM, CBC, or CTR mode. PBKDF2 key derivation, entirely in your browser.
- [Random Color Generator](https://zeroutil.com/tools/random-color-generator/) : Generate random colors with HEX, RGB and HSL values. Random color picker, colour randomizer and 5-color palette builder with history.
- [CSS Formatter / Minifier](https://zeroutil.com/tools/css-formatter/) : Format, beautify and minify CSS code.
- [World Clock](https://zeroutil.com/tools/world-clock/) : Live-updating clocks for multiple timezones. Add and remove cities to build your custom dashboard.
- [CSS Grid Generator](https://zeroutil.com/tools/css-grid-generator/) : Build CSS Grid layouts visually with live preview. Works as a grid system generator and HTML grid generator.
- [JSON Formatter](https://zeroutil.com/tools/json-formatter/) : Format, validate and minify JSON with syntax highlighting.
- [TOTP Generator](https://zeroutil.com/tools/totp-generator/) : Generate time-based one-time passwords (TOTP) from a base32 secret with live 30-second countdown.
- [Wallpaper Calculator](https://zeroutil.com/tools/wallpaper-calculator/) : Calculate wallpaper rolls needed for a room with pattern repeat, square-feet workflow, and metric/imperial conversions.
- [Image to Base64 Converter](https://zeroutil.com/tools/image-to-base64/) : Convert an image to a Base64 data URL or raw Base64 string for HTML, CSS, and API payloads. Runs in your browser.
- [Line Counter](https://zeroutil.com/tools/line-counter/) : Count total lines, blank lines and get line statistics.
- [Schema Markup Generator (JSON-LD)](https://zeroutil.com/tools/schema-markup-generator/) : Generate JSON-LD structured data for Article, FAQ, Product, Organization, LocalBusiness, HowTo, Recipe and Event.
- [XML Formatter / Validator](https://zeroutil.com/tools/xml-formatter/) : Format, beautify and validate XML with customizable indentation.
- [Flashcard Maker](https://zeroutil.com/tools/flashcard-maker/) : Create and study flashcards with front/back content, shuffle, and navigation.
- [Google SERP Preview](https://zeroutil.com/tools/google-serp-preview/) : Preview how your page appears in Google search results with character count indicators.
- [Neumorphism Generator](https://zeroutil.com/tools/neumorphism-generator/) : Create soft UI neumorphic shadows and effects.
- [Roman Numeral Converter](https://zeroutil.com/tools/roman-numeral-converter/) : Convert numbers to Roman numerals and Roman numerals to numbers.
- [Hreflang Tag Generator](https://zeroutil.com/tools/hreflang-tag-generator/) : Generate hreflang link tags for multilingual websites with x-default support.
- [Image Metadata Viewer](https://zeroutil.com/tools/image-metadata-viewer/) : View file info, dimensions, aspect ratio, and basic EXIF data from any image.

## Guides

- [AES-GCM vs AES-CBC: Which Mode to Use and Why](https://zeroutil.com/blog/aes-gcm-vs-cbc/) : What block cipher modes do, why GCM has mostly replaced CBC for new code, the IV and authentication rules that matter, and where each mode still earns its place.
- [Base64 Explained: What It Is, Why It Exists, and When Not to Use It](https://zeroutil.com/blog/base64-explained/) : A practical walkthrough of Base64 encoding — what it actually does to your bytes, why it's not encryption, and the handful of real places it still earns its keep in 2026.
- [Why Your PDF Tool Should Run in the Browser, Not the Cloud](https://zeroutil.com/blog/browser-pdf-tools-privacy/) : What actually leaks when you upload a PDF to a random online tool, what modern in-browser PDF libraries can genuinely do, and a checklist for before you upload anything sensitive.
- [Social Media Character Limits 2026: X, Bluesky, LinkedIn & More](https://zeroutil.com/blog/character-limits-social-2026/) : Current character limits for X, Bluesky, LinkedIn, Instagram, Threads, Mastodon and TikTok in 2026 - and how each counts emoji, URLs and multibyte text.
- [Client-Side Image Compression: What's Actually Happening in the Browser](https://zeroutil.com/blog/client-side-image-compression/) : How browsers compress images without touching a server — the real pipeline behind Canvas, OffscreenCanvas, and WebCodecs, and when it's not enough.
- [Compound Interest, Explained Like You Actually Have to Use It](https://zeroutil.com/blog/compound-interest-intuition/) : The math behind compound interest, why the Rule of 72 works, and why time matters more than rate for most real financial decisions.
- [Debugging Malformed JSON: A Field Guide](https://zeroutil.com/blog/debug-malformed-json/) : Every JSON parse error has a real cause hiding behind an unhelpful message. A practical guide to the five failure modes that produce 90% of the pain.
- [The Developer's JSON Guide: Everything Worth Knowing About JSON in 2026](https://zeroutil.com/blog/developer-json-guide/) : A comprehensive guide to JSON — the spec, the variants, the tooling, debugging, JWT and Base64 context, and how to ship systems that don't break on malformed payloads.
- [Flesch-Kincaid Explained: What the Score Means and How to Use It](https://zeroutil.com/blog/flesch-kincaid-explained/) : How the Flesch Reading Ease and Flesch-Kincaid Grade Level scores are computed, what they're good for, and the limits worth knowing before you optimize for them.
- [Hashing vs Encryption vs Encoding: The Three Things People Keep Confusing](https://zeroutil.com/blog/hashing-vs-encryption-vs-encoding/) : Encoding, encryption, and hashing get mixed up constantly, and the mistakes break real auth code. Here is the difference and when to use which.
- [JSON vs. JSON5 vs. JSONC: Which One and When](https://zeroutil.com/blog/json-vs-json5-vs-jsonc/) : Three formats that look nearly identical, behave completely differently, and produce a steady stream of parser errors when confused. A practical guide to telling them apart.
- [JWT Authentication Mistakes That Keep Appearing in Production](https://zeroutil.com/blog/jwt-authentication-mistakes/) : A tour of the JWT pitfalls that still ship to production in 2026 — algorithm confusion, weak secrets, missing expiry, and the subtle ways a library can fail open.
- [Never Paste This Into a Random Online Tool](https://zeroutil.com/blog/never-paste-sensitive-data/) : A practical threat model for developers and knowledge workers who use web tools at work. What's actually safe, what isn't, and what to do instead.
- [The Online Privacy Guide: Practical Threat Models for Browser-Based Work in 2026](https://zeroutil.com/blog/online-privacy-guide/) : A comprehensive guide to online privacy in 2026 — threat models, browser-based vs. cloud tools, passwords, encryption, and the habits that matter most.
- [Passkeys vs Passwords: How WebAuthn Actually Replaces the Password](https://zeroutil.com/blog/passkeys-vs-passwords/) : A grounded look at how passkeys, FIDO2, and WebAuthn work, why they kill phishing, and the real tradeoffs nobody mentions in 2026.
- [Password Strength in 2026: What Length and Character Sets Actually Buy You](https://zeroutil.com/blog/password-strength-2026/) : A practical look at entropy, NIST's current guidance, real GPU cracking speeds in 2026, and why passphrases beat forced complexity every time.
- [5 Common Percentage Mistakes and How to Avoid Them](https://zeroutil.com/blog/percentages-common-mistakes/) : Percentage points vs percent, symmetric vs asymmetric changes, markup vs margin - the five places percentage math quietly lies, and how to get them right.
- [How QR Codes Actually Work: A Practical Guide](https://zeroutil.com/blog/qr-codes-explained/) : What the squares mean, how error correction works, when to use which encoding mode, and why your printed QR code sometimes doesn't scan.
- [How to Calculate a Sale Discount: Formulas, Examples, and Common Traps](https://zeroutil.com/blog/sale-discount-math/) : The math behind percent off, stacked discounts, sales tax order, and the tricks retailers use to make a discount look bigger than it is.
- [The 90-Minute Sleep Cycle Rule: What It Actually Means](https://zeroutil.com/blog/sleep-cycles-90-minute-rule/) : How sleep cycles really work, why the 90-minute rule is a useful approximation, and how to time bedtime so you wake up between cycles instead of mid-cycle.
- [Unix Timestamps and Timezones: The Confusion That Eats Your Week](https://zeroutil.com/blog/unix-timestamps-timezones/) : A practical walkthrough of Unix time, timezones, daylight saving time, and the handful of patterns that keep teams from shipping date bugs to production.
- [How US Federal Tax Brackets Work (2024 Guide)](https://zeroutil.com/blog/us-tax-brackets-2024/) : Marginal vs effective tax rates, how the brackets stack, what your 'tax bracket' actually means, and the worked example most people get wrong.
- [UUID vs ULID vs NanoID: Picking an ID Scheme in 2026](https://zeroutil.com/blog/uuid-ulid-nanoid/) : A practical comparison of UUIDv4, UUIDv7, ULID, and NanoID for sortability, index performance, size, and collision odds, with a clear decision guide.
- [WCAG 2.2 Color Contrast: Hitting AA Without Guessing](https://zeroutil.com/blog/wcag-color-contrast/) : A practical guide to WCAG 2.2 contrast ratios - the AA and AAA thresholds, the luminance math, why the formula is flawed, and how APCA fixes it.
- [What Counts as a Word? Punctuation, Emoji, Hyphens & Contractions](https://zeroutil.com/blog/what-counts-as-a-word/) : Do hyphenated words, contractions, and emoji count as one word? How Microsoft Word, Google Docs, and style guides count punctuation, dashes, and Unicode.

## About

- [About ZeroUtil](https://zeroutil.com/about/) : Mission, tool philosophy, and privacy-first approach
- [Methodology](https://zeroutil.com/methodology/) : How we build, test, and maintain our tools