Free Online Utilities

A growing collection of fast, no-nonsense tools for DNS, email deliverability, network diagnostics, privacy and everyday developer tasks.

Tip: press / or the search icon in the header to find any tool.

DNS & Domain

DNS Lookup Dig-style lookup for A, AAAA, MX, TXT, NS, SOA, SRV, CAA, PTR — plus subdomain sweep. DNS Propagation Query one record across 14 public resolvers in the US and worldwide to spot propagation lag. Reverse DNS Lookup Resolve an IPv4 or IPv6 address to its PTR hostname (reverse DNS). WHOIS Lookup Registration, registrar, dates and nameservers for a domain (live WHOIS).

Email & Deliverability

SPF Checker Fetch an SPF record and recursively count DNS lookups against the 10-lookup limit. DMARC Checker Read and explain a domain's DMARC policy (p, rua, pct, alignment). DKIM Checker Look up a DKIM public key by selector and domain. MX Lookup List a domain's mail servers in priority order. Blacklist Check Check an IP against major DNS blacklists (RBLs). Email Verifier Validate an address: syntax, domain MX, role/disposable, live mailbox probe. Email Header Analyzer Paste raw email headers to trace delivery hops and delays. Email Health Check One domain, one click: MX, SPF, DMARC, DKIM, reverse DNS and blacklist checks together. Email Normalizer Reduce an email address to its canonical form (Gmail dots, plus-tags). SPF Record Generator Build a valid SPF (v=spf1) record from your senders, includes and policy. DMARC Record Generator Build a DMARC policy record with reporting and alignment options.

Network & Security

SSL Certificate Inspect a site's TLS certificate: issuer, validity, SANs and expiry. HTTP Headers View a URL's response headers and follow its redirect chain. Security Headers Grade a site on HSTS, CSP, X-Frame-Options and other security headers. Port Checker Test whether common or custom TCP ports are open on a host. IP Info Reverse DNS plus ASN, network and country for an IP (via Team Cymru). URL Redirect Checker Trace a URL's full 301/302/307/308 redirect chain to its final destination. Meta Tags Checker Inspect a page's title, meta description, canonical and Open Graph / Twitter Card tags. IP Address Converter Convert an IPv4 address between dotted, decimal, hex and binary, or expand IPv6. HTTP Status Codes A searchable reference of every HTTP status code and what it means. IPv4 Range Expander Expand a CIDR block or start-end pair into its full IP range. Basic Auth Generator Build an HTTP Basic Authorization header from a username and password. TOTP / 2FA Generator Generate time-based one-time passwords from a TOTP secret to verify 2FA. RSA Key Pair Generator Generate an RSA public/private key pair in your browser via WebCrypto. CSR / Certificate Decoder Paste a CSR or certificate PEM and read its subject, SANs, key and validity. IPv6 Subnet Calculator Work out the network, address range and count for an IPv6 prefix. MAC Address Lookup Identify a device manufacturer from its MAC address and format it.

Privacy & Identity

What Is My IP See your public IP address, reverse DNS and network (ASN) — what every site sees. Browser Privacy Check See the fingerprint your browser exposes: user agent, screen, fonts, canvas, WebGL and more. User Agent Parser Break a User-Agent string into browser, engine, OS and device type. HTTP Request Headers Show the HTTP headers your browser sends to every website you visit. Credit Card Validator Check a card number with the Luhn algorithm and detect its network. IBAN Validator Validate an IBAN checksum and break out its country, bank and account parts.

Encoding & Data

JWT Decoder Decode a JSON Web Token's header and payload, and verify HMAC (HS256/384/512) signatures. HMAC Generator Compute an HMAC (SHA-256/512, SHA-1, MD5) from a key and message. Base64 Encode or decode Base64 text. URL Encode/Decode Percent-encode or decode URL/query strings. Hash Generator MD5, SHA-1/256/384/512, SHA3-256/512, RIPEMD-160 and CRC32 of any text. JSON Formatter Pretty-print, validate or minify JSON. Punycode / IDN Convert internationalized domains between Unicode and punycode (xn--). JSON to CSV Converter Convert JSON arrays to CSV and CSV back to JSON, right in your browser. JSON to YAML Converter Convert between JSON and YAML both ways, entirely client-side. XML to JSON Converter Convert XML to JSON and JSON to XML in your browser. AES Encrypt / Decrypt Encrypt or decrypt text with AES-256-GCM and a passphrase, all in your browser. JSON Minify Strip whitespace from JSON to produce the smallest valid output. JSON Escape / Unescape Escape text into a JSON string literal, or unescape one back to raw text. MIME Type Lookup Look up the MIME content type for any file extension and vice versa. JSON Diff Compare two JSON documents and highlight added, removed and changed keys.

Developer Tools

Regex Tester Test a regular expression against sample text, see matches and groups, or run a replace. Password Strength Estimate how strong a password is: entropy and crack-time. Bcrypt Hash & Verify Generate a bcrypt password hash, or verify a password against one. Cron Explainer Translate a cron expression into plain English and list its next run times. UUID Generator Generate UUID v4 (random) or v7 (time-ordered) values in bulk. Chmod Calculator Convert Unix file permissions between symbolic, octal and checkbox form. Timezone Converter Convert a date and time between world time zones, with a live world clock. Password Generator Create strong random passwords with adjustable rules. Subnet Calculator IPv4 CIDR maths: network, broadcast, mask, host range and count. Epoch Converter Convert between Unix timestamps and human dates. XML Formatter Pretty-print and indent XML, or minify it to a single line. SQL Formatter Beautify and indent SQL queries with keyword casing and dialect options. HTML Beautifier Format messy HTML for readability, or minify it. CSS Beautifier Pretty-print or minify CSS with consistent formatting. JavaScript Beautifier Format or minify JavaScript source code. Cron Expression Generator Build a crontab expression from schedule pickers with a live preview. cURL Command Builder Assemble a cURL command from method, URL, headers and body. Docker Run to Compose Convert a docker run command into a docker-compose.yml snippet.

Text & Conversion

Color Converter Convert colours between HEX, RGB and HSL with a live preview. Case Converter Convert text between UPPER, lower, Title, camelCase, snake_case and kebab-case. HTML Entity Encoder Encode or decode HTML entities like & and ©. Number Base Converter Convert numbers between binary, octal, decimal and hexadecimal. Text Compare Compare two blocks of text and highlight the differences line by line. Markdown to HTML Render Markdown to clean, sanitized HTML with a live side-by-side preview. Word Counter Count words, characters, sentences, paragraphs and reading time. Slugify Turn a title into a clean, URL-friendly slug. Lorem Ipsum Generator Generate placeholder Lorem Ipsum paragraphs, sentences or words. Sort Text Lines Sort lines alphabetically, numerically or reversed. Remove Duplicate Lines Strip duplicate lines from a block of text. URL Parser Break a URL into scheme, host, path, query and fragment. Roman Numeral Converter Convert between Arabic numbers and Roman numerals. Unit Converter Convert length, weight, temperature and data-size units. Percentage Calculator Solve everyday percentage questions quickly. Color Contrast Checker Check colour contrast against WCAG AA and AAA thresholds. CSS Gradient Generator Design linear and radial CSS gradients and copy the code. Box Shadow Generator Build CSS box-shadow values with a live preview. HTML to Markdown Convert HTML into clean Markdown, right in your browser.

Image

QR Code Generator Turn any text or URL into a QR code and download it as PNG or SVG. Image to Base64 Encode an image to a Base64 data URI (or decode one back) without uploading it. WiFi QR Code Generator Make a QR code that joins a WiFi network from SSID and password. Image Format Converter Convert images between PNG, JPG and WebP in your browser. Image Resizer Resize images to target dimensions in the browser.

Calculators

Calculator A simple online calculator with the four basic operations and percent. Scientific Calculator Trigonometry, logarithms, powers, roots and constants with memory. Fraction Calculator Add, subtract, multiply and divide fractions and simplify the result. PEMDAS Calculator Solve any expression step by step, line by line, in order of operations with each move explained. GPA Calculator Calculate weighted or unweighted GPA from grades and credit hours. Discount Calculator Work out the sale price and how much you save from a percentage off. Tip Calculator Calculate a tip and split the bill between any number of people. Sales Tax Calculator Add or remove sales tax / VAT from a price at any rate. Loan Calculator Monthly payment and total interest for a loan, with an amortization schedule. Mortgage Calculator Estimate a mortgage payment including taxes, insurance and PMI. Compound Interest Calculator Project savings growth with compounding and regular contributions. BMI Calculator Calculate Body Mass Index in metric or imperial units with category. Calorie Calculator Estimate daily calories (TDEE) from the Mifflin-St Jeor equation.

Date & Time

Age Calculator Find an exact age in years, months and days, and days until the next birthday. Days Between Dates Count the days, weeks and months between two dates. Date Calculator Add or subtract days, weeks, months or years from a date. Days Until Date Count down the days until a future date or event. Hours Calculator Work out the hours and minutes between two times, with a break deduction. Countdown Timer A full-screen countdown timer with an alarm when it finishes. Online Stopwatch A precise online stopwatch with lap times.

Generators & Random

Random Number Generator Generate random numbers in a range, with options for count and uniqueness. Dice Roller Roll one or more dice (D4 to D20 or custom sides). Coin Flip Flip a virtual coin and track heads/tails streaks. List Randomizer Shuffle a list, pick winners or split it into random teams. Powerball Number Generator Generate random Powerball numbers: 5 from 1-69 plus a Powerball from 1-26. Mega Millions Number Generator Generate random Mega Millions numbers: 5 from 1-70 plus a Mega Ball from 1-24. Lottery Number Generator Generate random lottery numbers for any game: pick the range, how many, and an optional bonus ball.

Frequently asked questions

Are these tools free to use?

Yes. Every tool on this site is completely free, with no sign-up, no account and no usage limits beyond basic anti-abuse rate limiting. There are no ads.

Do you store the domains, IPs or text I look up?

No. Nothing you enter is written to a database or a file. Queries run in memory and results are returned straight to your browser. We use privacy-respecting analytics (Google Analytics) to count visits, but the specific values you look up are never stored, logged or sold.

What can I do with these utilities?

You can diagnose DNS and email deliverability problems (SPF, DKIM, DMARC, MX, blacklists), inspect SSL certificates and HTTP headers, check open ports, and run everyday developer conversions like Base64, hashing, JSON formatting and subnet maths.

Do I need to install anything?

No. Everything runs in your browser against our server — there is nothing to download or install, and it works on desktop and mobile.

Do these tools work on mobile phones and tablets?

Yes. The site is responsive and every tool works in any modern mobile or desktop browser, so you can diagnose DNS, email or TLS issues from a phone just as easily as from a laptop.

Is there an API I can call from scripts?

These tools are designed for interactive use in the browser rather than as a public API. For automation, most of the underlying checks map to standard command-line tools such as dig, openssl and curl.

Why are some lookups slightly slow?

Live checks like DNS, WHOIS, SSL and port tests query real remote servers, so the response time depends on those servers and the network. Pure conversions such as Base64 or JSON formatting return almost instantly.

Can I use these tools for commercial work?

Yes. You are free to use them for personal, educational or commercial projects at no cost, subject only to basic rate limiting to keep the service available for everyone.