Developer tools
AI Token Cost Calculator
Estimate and compare API costs across 8 current AI models — paste a prompt or enter token counts directly, no sign-up.
Bandwidth Calculator
Calculate file transfer time from size and connection speed — with a realistic estimate (adjustable efficiency, default 80%) shown alongside the theoretical one, not just a theoretical number presented as if it were real.
Base64 Encoder/Decoder
Encode text or files to Base64, or decode Base64 back to text or an image preview — both directions on one page, with an optional URL-safe variant.
bcrypt Hash Generator
Hash a password with bcrypt live, entirely in your browser, with an adjustable cost factor — plus a Verify tab to check a candidate password against an existing hash.
BIP39 Mnemonic Generator
Generate a 12–24 word BIP39 mnemonic and validate any phrase's checksum, in a page with no wallet-address derivation, no client-configuration clutter, and a warning that stays visible instead of buried in the fine print. Testing and learning only — not for real funds.
chmod Calculator
Toggle read/write/execute for owner, group, and others — including setuid, setgid, and sticky bit from the start, not gated behind a separate "Pro" tool — and get a ready-to-copy chmod command instantly.
Code to Image Converter
Turn a code snippet into a syntax-highlighted window image — auto-sized to your code so there's no manual centering, and your code never touches the URL (unlike the tools it's compared to, where pasting code puts it straight into a query string or hash you can verify yourself).
Cron Expression Parser
Type a 5-field cron expression and get a plain-English description plus the next 10 run times in your browser's local timezone (shown explicitly) — not just 5, and not silently assuming server time.
CSS Minifier / Formatter
Minify or format CSS live, with an instant byte-size reduction percentage — /*! license */ comments always survive minification, and declaration order is never changed.
CSV Doctor
Paste or upload a CSV and get a live health report — delimiter, column-count mismatches, exact duplicate rows, and possible encoding mismatches — with opt-in cleanup that never deletes data without your say-so.
Data Size Converter
Convert between bits, bytes, KB, MB, GB, and TB — with decimal (1000-based) and binary (1024-based, KiB/MiB/GiB) values shown side by side, so you can see exactly why your "500GB" drive shows up as 465 in your OS.
HMAC Generator
Compute an HMAC from a message and secret key live, with an explicit key encoding selector (UTF-8, Hex, or Base64) to avoid the most common cause of mismatched results.
HTML Entity Encoder/Decoder
Encode text to safe HTML entities or decode entities back to text live as you type — decoding covers numeric entities and around 100 common named entities like © and ™, not just the basic 5.
HTML Minifier / Formatter
Minify or format HTML live, with an instant byte-size reduction percentage — content inside pre, textarea, script, and style tags is always preserved byte-for-byte.
HTTP Status Code Reference
Search every standard HTTP status code by number or name, with a plain-English summary first (not just raw RFC text), plus explicit "often confused with" notes for pairs like 401 vs 403 and 502 vs 503 vs 504.
IP Subnet Calculator
Paste a CIDR address (192.168.1.0/24) in one field — no separate IP and subnet-mask dropdown — and get the network, broadcast, and usable host range, with /31 (RFC 3021 point-to-point) and /32 (single host) handled correctly instead of the naive formula that gets both wrong.
JavaScript Minifier / Formatter
Minify or format JavaScript live, powered by terser — the same industry-standard parser used by major bundlers — so your code's behavior is never changed, and /*! @license @preserve comments always survive.
JSON Formatter & Validator
Format, validate, and explore JSON — beautify, minify, and a collapsible tree view, all on one page with no submit button.
JSON to CSV Converter
Convert JSON to CSV live — no button. Automatically finds the array of objects to convert (and tells you which field it used), and flattens nested objects and arrays with one consistent, predictable rule.
JSON to TOML Converter
Paste JSON and get TOML instantly — nested objects become [section] headers, arrays of objects become [[array-of-table]] blocks, and TOML's real constraints (no null, no mixed-type arrays) are flagged clearly instead of silently producing invalid output.
JSON to YAML Converter
Paste JSON and get YAML instantly, no Convert button — with ambiguous strings like "yes" or "12:00:00" automatically quoted so they don't get silently reinterpreted as booleans or times when the YAML is read back.
JSON Tree Viewer
Explore JSON as a live, collapsible tree — click any node to see and copy its JSONPath, no button to click, and the top level opens automatically while nested branches stay collapsed for large files.
JWT Encoder/Decoder/Verifier
Decode a JWT's header and payload instantly, see exp/iat as readable dates with expiry status, and verify an HS256 signature — entirely in your browser, with zero network requests.
MD5 Hash Generator
Generate an MD5 hash from text or a file live, entirely in your browser — for checksums and file-integrity checks only, never for password storage.
Meta Tag & Open Graph Generator
Generate basic SEO meta tags, Open Graph tags, and Twitter Card tags all at once from a title, description, URL, and image — with a live preview of how the link card looks on X and Facebook, so you never forget the tag that tanks your click-through rate.
MIME Type Lookup
Look up a file extension or MIME type — with the standard value plus any legacy/nonstandard alternates actually seen in the wild, an explicit note where a widely-used server's default config disagrees with the current spec (like nginx still serving .js as application/javascript), and a fallback explanation for extensions that aren't registered at all.
React Native Shadow Generator
Tune a shadow with live iOS and Android previews — Android's opacity falls off exponentially as elevation increases, not linearly like most generators assume — and copy Platform.select-wired StyleSheet.create code, ready to paste.
Regex Tester
Test a JavaScript regular expression against any text — matches highlight live, and every match lists its numbered and named capture groups. Uses your browser's native regex engine, not a separate flavor to translate mentally.
RSA Key Pair Generator
Generate an RSA public/private key pair entirely in your browser, in PEM format — only 2048-bit and up, no weak key sizes offered.
SHA1 Hash Generator
Generate a SHA-1 hash from text or a file live, entirely in your browser — with no arbitrary file size cap, and a clear warning that SHA-1 shouldn't be used for security purposes.
SHA-224 Hash Generator
Generate a SHA-224 hash from text or a file live, on one page — no ads, no button, and a clear warning that raw hashes like this shouldn't be used for password storage.
SHA-256 Hash Generator
Generate a SHA-256 hash from text or a file live, on one page, entirely with your browser's own Web Crypto API — nothing is ever transmitted anywhere.
SHA-384 Hash Generator
Generate a SHA-384 hash from text or a file live, and compare it against an expected checksum instantly — useful for verifying a downloaded file's integrity.
SHA-512 Hash Generator
Generate a SHA-512 hash from text or a file live, and compare it against an expected checksum instantly — useful for verifying a downloaded file's integrity.
Unix Timestamp Converter
Convert Unix timestamps to dates and back, live as you type, with a timezone picker and a running current-timestamp display.
ULID Generator
Generate up to 1000 ULIDs at once with the embedded timestamp shown next to each one — no separate decode page — plus ULID-to-UUID and UUID-to-ULID conversion on the same screen.
URL Encoder/Decoder
Encode or decode URLs and query parameters live as you type — choose between component and full-URL encoding, with a clear message instead of a crash on malformed input.
URL Parser
Break down any URL into protocol, credentials, hostname (with Unicode alongside punycode for international domains), port, path, hash, and every query parameter — including every occurrence of a repeated key, not just the last one.
User-Agent Parser
Break a User-Agent string down into browser, engine, OS, and device type — and get flagged when it matches Chrome's frozen mobile pattern ("Android 10; K"), so a fixed placeholder value isn't mistaken for the device's real OS version or model.
UUID v4 Generator
Generate cryptographically random UUID v4 values, one or up to 100 at once, with uppercase and no-hyphen format options.
YAML to JSON Converter
Paste YAML and get JSON instantly — anchors and aliases are fully resolved (not left as an unsupported error), and a tab-character indentation mistake is pointed out by exact line number instead of a cryptic parser message.
From the blog
Your "500GB" drive shows up as 465. Most converters won't tell you why — ours shows both numbers at once.
Storage makers use decimal GB, operating systems report binary GiB, and the two get the same nickname. We show decimal and binary side by side with a note on why they differ, instead of picking one silently.
2026-09-09 Forget one tag and your shared link loses its image on X. We generate it by default so you can't.
Basic meta, Open Graph, and Twitter Card tags are usually three things to remember separately. Ours generates all three from one form, and defaults twitter:card to summary_large_image the moment you add an image.
2026-09-09 The Cheapest AI Model Per Token Isn't Always the Cheapest Per Task — Here's a Calculator That Compares 8 of Them
AI API prices dropped roughly 80% between early 2025 and early 2026, and now span a 1,400x range between the cheapest and priciest models. We built a calculator to estimate and compare costs across 8 current models — and to flag the catch that per-token price alone can miss.
2026-09-03 Most JSON tree viewers make you click a button, then count brackets by hand to find a value's path. Ours gives you both instantly.
We checked jsonlint.com's tree viewer directly — it needs a 'View Tree' click before anything renders, and clicking a node never tells you its path. Ours renders live as you type, and clicking any node shows (and lets you copy) its exact JSONPath.
2026-08-30 Most JSON-to-CSV converters grab the first array they find — even if it's the wrong one. Ours actually looks for the right data.
We checked convertcsv.com directly — it's a multi-step 'Step 3: Generate output' flow, not live. And a documented failure mode in this category is picking the first array in a file even when it's just metadata. Ours searches for an actual array of objects, tells you which field it used, and flattens nested data with one predictable rule.
2026-08-30 A tool named CSVDoctor lists 6 validation checks. Duplicate rows isn't one of them.
We checked csvdoctor.pages.dev and jsontotable.org's CSV fixer directly. Neither documents duplicate row detection, and one runs a paste-scan-fix flow instead of updating live. We also skipped the black-box 'auto-fix' approach to encoding — this tool lets you see the same file decoded five different ways and pick the one that actually reads correctly.
2026-08-30 A JSON to YAML converter that doesn't quote "yes" will hand you a YAML bug later
JSONLint's converter needs a button click. Several others skip quoting strings that YAML reads as booleans or times. We checked both, then built one that fixes both by default.
2026-08-30 Most JSON to TOML converters let a mixed-type array through. TOML doesn't actually allow that.
TOML has two real constraints most tools gloss over: no native null, and arrays can't mix types. We built a converter that stops and tells you exactly which field is the problem.
2026-08-30 The YAML error that's actually an invisible tab character, explained by line number
YAML forbids tabs for indentation, but tabs and spaces look identical in most editors — so the parser error rarely points at the real problem clearly. We check for it directly.
2026-08-30 regex101 makes you pick from seven regex flavors. Your browser only runs one.
PCRE2, Python, Go, Java, .NET, Rust, POSIX — regex101 supports all of them, which is powerful and also a question most web developers don't need to answer.
2026-08-30 crontab.guru shows the next 5 run times. When a schedule misbehaves, that's not enough.
Debugging a cron job that fires at the wrong time usually means scrolling forward to spot the pattern. Five run times often isn't enough runway to see it.
2026-08-30 setuid, setgid, and the sticky bit are usually in the "Pro" chmod calculator, not the free one
Several chmod tools split their basic checkbox calculator from an "Advanced" or "Pro" version that actually handles special permission bits. We put them in the same tool.
2026-08-30 Most ULID generators split generate, decode, and UUID conversion into separate pages. We didn't.
One ULID site only generates one at a time and buries bulk generation on a separate page. Another has no decoder at all. We put generation, timestamp decoding, and UUID conversion on one screen.
2026-08-30 BIP39 tools bolt on address derivation, client configs, and clone-site branding. We left all of it out.
The best-known BIP39 tool has been cloned under near-identical names, and its full-featured forks bury a real security warning under derivation paths and client settings. We kept this one narrow on purpose.
2026-08-30 Paste code into a popular code-screenshot tool, then look at your address bar
We pasted a fake secret into two well-known code-to-image tools and checked the URL. It was right there both times — once in plain text, once base64-encoded. We built this so that can't happen.
2026-08-30 Most React Native shadow generators fade Android's elevation in a straight line. Real Android doesn't.
A developer wrote a whole post about fixing a shadow generator that used linear interpolation for Android elevation, when real elevation opacity falls off exponentially. We built that curve in from the start.
2026-08-30 The one-liner that quietly deletes half your query parameters
Object.fromEntries(url.searchParams.entries()) is a natural way to turn parsed query params into an object. We ran it on a URL with a repeated key and watched a value disappear.
2026-08-30 "Android 10; K" isn't a real device — it's what Chrome shows everyone now
Since Chrome 110, most mobile User-Agent strings report a fixed, fake OS version and device model. A parser that doesn't flag this is quietly handing you placeholder data as if it were real.
2026-08-30 httpstatuses.com — the site half the internet links to — now redirects to a marketing glossary
We visited the URL directly. It's not down, not parked — it redirects straight to an unrelated site's web development glossary page. Every old link to it is quietly broken.
2026-08-30 The world's most popular web server still serves .js with the wrong MIME type
RFC 9239 settled it in 2022: .js should be text/javascript. nginx's own default config still says application/javascript. A lookup tool that shows only one of those is only half right.
2026-08-30 The subnet math you learned in school says a /31 has zero usable hosts. RFC 3021 says otherwise.
2^(32-prefix) - 2 is the formula everyone memorizes. Plug in a /31 and it gives you zero. The actual standard for point-to-point links says both addresses are usable.
2026-08-30 A download time calculator that admits its own number isn't realistic — then gives you only that number anyway
One existing tool labels its comparison chart "not necessarily realistic values," then hands you a single theoretical download time with no realistic alternative in sight.
2026-08-30 Paste a bare % into most URL decoders and you get a blank screen or a raw JavaScript error. Ours tells you what's wrong.
One popular URL encoder only goes live once you manually flip on a "Live mode" setting. Another shows ad-personalization cookies. And a lot of simple wrapper tools crash outright on malformed percent-encoding. Ours is live from the first keystroke and never throws a raw error at you.
2026-08-29 Two HTML entity tools we checked only decode numeric entities. Type © into either one and it just sits there, unconverted.
We tested two free HTML entity decoders directly: both handle the 5 basic characters and decimal codes, but neither converts ©, ™, or ♥ back to real characters. Ours decodes around 100 common named entities on top of numeric ones — live, no button.
2026-08-29 A security write-up on JWT decoders warns that tools offering signature verification are more likely to process your token server-side. Ours proves it doesn't, in your own DevTools.
Pasting a JWT into the wrong tool can leak whatever's in its claims — user IDs, emails, permissions. A write-up on this exact risk says trustworthy decoders should let you verify the privacy claim yourself. Ours tells you to open the Network tab and check, because there's nothing to hide.
2026-08-29 One MD5 tool literally recommends it for "encoding passwords." That advice can get real accounts compromised — ours warns against it instead.
We checked a popular MD5 generator directly: its own page describes the tool as useful for encoding passwords and credit card numbers. MD5 has no salt and is trivially fast to brute-force — that's dangerous advice. Ours puts a clear warning front and center, and adds file hashing for the checksum use case MD5 is actually good for.
2026-08-29 One SHA-1 generator we checked never mentions that SHA-1 is cryptographically broken. Another caps files at 50MB for no real reason.
SHA-1 has had a practical collision attack since 2017, but sha1-online.com's page doesn't mention it anywhere. A tool that does warn about it still needs a button click and stops at 50MB files. Ours warns clearly, updates live, and doesn't cap file size.
2026-08-29 Search results describe SHA-224 tools as good for "password hashing." A raw hash with no salt still isn't. Ours says so, and keeps text and file hashing on one page.
SHA-224 tooling write-ups list password hashing as a use case, which undersells the risk of using a raw, unsalted hash for credentials. One popular tool also splits text and file hashing into two separate pages and runs ads on both. Ours keeps it on one page, warns clearly, and skips the ads.
2026-08-29 A SHA-256 tool with a 3.0/5 rating from 1,900+ votes doesn't explain whether your input is processed locally or sent to a server. Ours states it outright.
We checked two SHA-256 tools directly: one needs a settings toggle for live updates and splits file hashing onto a separate page, the other uses Start/Stop buttons and never clarifies where your data actually goes. Ours is live, one page, and says plainly: nothing is ever transmitted.
2026-08-29 One SHA-384 tool lets you compare against an expected hash but can't hash files. Another hashes files but has no comparison. We checked — nobody does both.
Checking a downloaded file's integrity means hashing the file and comparing it to a published checksum. We found tools that do one half or the other, but not both together. Ours hashes files live and compares against an expected value on the same page.
2026-08-29 SHA-512 is the most common checksum for large downloads, and one popular generator still needs a settings toggle to update live.
We checked a widely-used SHA-512 tool directly: real-time updates require flipping on "Auto Update" first, ads run through the page, and file hashing lives on a separate URL. Ours is live by default, ad-free, and keeps text, file, and checksum comparison on one page.
2026-08-29 The same secret key can produce a different HMAC on different tools, and it's rarely a bug in your code. It's key encoding, and most tools never let you choose.
A common, well-documented gotcha: some HMAC tools read your key as UTF-8 text, others as hex or Base64 bytes, silently producing different results for the same-looking string. We checked a popular generator that also needs a button and shows ads. Ours is live, ad-free, and lets you pick the key encoding explicitly.
2026-08-29 One bcrypt tool processes your actual password on its server. And bcrypt itself silently drops anything past 72 bytes — nobody we checked warns about it.
We checked a popular bcrypt generator directly: it states outright that hashing happens server-side, meaning your real password gets sent over the network. Separately, bcrypt has a well-documented 72-byte limit that silently truncates long or multi-byte passwords — no tool we found flags it. Ours does both right.
2026-08-29 A popular RSA key generator lets you pick 512-bit — a size that's actually been cracked in the real world. Ours doesn't offer it.
We checked two RSA key generators directly: one never warns against using its keys in production, the other offers 512-bit RSA with no caveat at all, despite it being publicly broken. Ours starts at 2048-bit, the NIST-recommended minimum, and says plainly what these keys are and aren't for.
2026-08-29 There's a real GitHub issue about a minifier mangling the whitespace inside <pre> tags. We wrote a test to make sure ours never does that.
HTML minifiers have a documented failure mode: touching whitespace inside <pre>, <textarea>, or <script> tags, which can break rendering or behavior. We checked two popular tools — both need a button click. Ours is live and we tested, byte-for-byte, that protected content survives untouched.
2026-08-29 Some CSS minifiers offer to alphabetize your declarations. That can silently change which style wins. Ours never touches the order.
A declaration-sorting feature sounds harmless until you have a duplicated property relying on cascade order — then it can flip which value actually applies. We also checked a popular minifier that needs a button click. Ours is live, keeps your declaration order exactly as written, and preserves /*! license */ comments the way YUI Compressor and CSSO do.
2026-08-29 A regex-based JS minifier can quietly break your code. We used the same parser major bundlers use instead.
Minifying JavaScript means understanding real syntax — string literals, regex literals, automatic semicolon insertion — not just stripping whitespace with regular expressions. We checked a popular minifier that needs a button click, then built ours on terser, the industry-standard parser, so behavior never changes and /*! @license comments always survive.
2026-08-29 One popular epoch converter makes you click a link to change the year. Ours just takes a date.
A real user review of a popular epoch converter says they had to click a 2024 link to reach 2025. Ours takes any timestamp or date directly, converts live, and switches timezones without a button.
2026-08-28 The most popular UUID generator tells you to refresh the page for a new one. Ours has a button.
The default UUID generator most people land on has no format options and literally says 'refresh page to generate another.' Ours regenerates instantly, in bulk, with uppercase and no-hyphen toggles.
2026-08-28 JSONLint makes you click Validate. Ours validates while you type.
The most-cited JSON tools split formatting, pretty-printing, and tree view across separate pages, run ads, and slow down on large files. Ours does all three in one page, live, with no submit button.
2026-08-28 Base64 encode and decode are usually two different websites. We put them on one page.
The most common Base64 tools split encoding and decoding across separate sites, run ads above the result, and fail silently on image data. Ours does both directions, previews decoded images, and stays ad-free.
2026-08-28