Tools for websites, SEO, programming, data and colors. Choose a tool and read its instructions, examples and limits before you begin.

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SEO and webmaster

IPv4 and IPv6 subnet calculator

Find the network, address range, subnet mask and address count from an IP address and CIDR prefix. Includes IPv4 point-to-point networks and IPv6.

What is my IP?

See the public IP address this website receives and whether it uses IPv4 or IPv6. Copy your IP and refresh it after changing your network or VPN.

UTM builder for campaign URLs

Build links with UTM parameters for your campaigns. Set source, medium and campaign name, review the generated URL and copy it for use.

DNS lookup: check a domain’s DNS records

Look up a domain’s A, AAAA, MX, TXT, NS, CNAME and CAA records. Inspect responses and errors without treating one resolver as a global propagation test.

WHOIS lookup: public domain data with RDAP

Look up a domain’s published registrar, dates, status and nameservers with RDAP. Redacted or unavailable registration fields remain clearly identified.

Security headers check: inspect HTTP responses

Inspect a page’s CSP, HSTS and other HTTP response headers. Read actual values and contextual explanations; this check does not certify website security.

Broken link checker: find links and source pages

Crawl your site with HTML and JavaScript to find broken links and missing resources. Review source pages and redirects, then download the CSV report.

Open Graph checker and social preview

Check a page’s Open Graph title, description, URL and image. See an illustrative sharing preview and identify missing or duplicate metadata.

Robots.txt tester: check URLs and user agents

Test robots.txt rules for a URL and user agent. See the matching allow or disallow rule; crawl permission alone does not guarantee search indexing.

Schema markup generator for JSON-LD

Choose a Schema.org type, fill in its fields and generate JSON-LD. Copy the code and check that it describes the content shown on your page.

Robots.txt generator

Create a robots.txt file with user agents, allowed or blocked paths and sitemap URLs. Review the rules before copying or downloading the file.

Hreflang tag generator

Enter equivalent page URLs and language or region codes. Generate reciprocal hreflang tags with an optional x-default version for review.

Google SERP simulator

Preview a Google-style snippet using your title, URL and meta description. Compare mobile and desktop and estimate title width.

XML sitemap generator

Create an XML sitemap from a URL list or by crawling your website. Review discovered pages, edit the list and download your sitemap.xml file.

HTTP redirect checker

Check a URL’s HTTP redirects, status codes and final destination. Follow each step in the redirect chain and identify loops or unexpected hops.

SSL certificate checker

Check a domain’s SSL certificate, expiry date, issuer and covered hostnames. Review the validity and details of the website’s TLS certificate.

SPF, DKIM and DMARC checker

Check your domain’s SPF, DKIM and DMARC DNS records. Enter a DKIM selector to review email authentication syntax, configuration and policies.

Programming and data

HTML entity encoder and decoder

Encode HTML characters and decode numeric and named references. Results remain text and never execute HTML.

HTML formatter and beautifier

Indent HTML fragments while preserving attributes, text and pre, script and style blocks. Copy the code and review whitespace.

JSON compare: structural diff

Compare two JSON documents independently of object key order. Find additions, removals and changes using JSON Pointer paths.

Binary translator and number converter

Convert decimal numbers to binary and back, or translate UTF-8 text into binary bytes. Copy or download the result in your browser.

Unix timestamp converter

Convert Unix timestamps to UTC dates and back, in seconds or milliseconds.

JWT decoder

Read a JWT’s JSON header and payload locally without sending the token elsewhere.

JSON to CSV and CSV to JSON converter

Convert JSON arrays into CSV tables and CSV files into JSON. Choose the delimiter and header options, check the data and download the result.

JSON to YAML and YAML to JSON converter

Convert JSON to YAML or YAML to JSON. Check syntax, choose indentation and copy or download the converted data for your configuration files.

XML formatter and syntax checker

Make XML easier to read with consistent indentation and find syntax errors. Copy the formatted result or download it as a file.

JSON formatter

Format or minify JSON while preserving numbers and duplicate keys. Browser processing: 1 million input characters, 100 nesting levels, 4 million output characters.

JSON validator

Validate JSON syntax and locate errors by line and column. Does not validate JSON Schema and allows duplicate keys. Up to 1 million characters and 100 levels.

Base64 converter

Encode and decode UTF-8 text with standard Base64 or Base64url. Text up to 200,000 characters; Base64 strings up to 1 million. Binary files not supported.

Regex tester

Test JavaScript regex with groups and indices. Isolated worker, 1 second limit, 100,000 text characters, 1,000 results and 500,000 captured characters. Not PCRE.

Online SQL formatter

Format SQL queries with readable indentation. Choose a supported SQL dialect, copy the formatted result and organize code without running queries.

CSS and JavaScript minifier

Minify CSS or JavaScript code, compare the original and output sizes, and copy the result. Select your language and reduce the size of your code.

Chmod permissions calculator

Convert Linux file permissions between numeric and symbolic notation. Set read, write and execute permissions for the owner, group and others.

Web design and colors

Color contrast checker for WCAG

Compare foreground and background colors. Calculate their contrast ratio and check WCAG AA and AAA thresholds for normal and large text.

Favicon generator

Create favicons from an image, text or emoji. Preview and download several PNG sizes and an ICO file, with image processing in your browser.

Color palette generator

Generate analogous, complementary, triadic and monochromatic color palettes. Copy HEX codes and download the palette as CSS variables.

CSS gradient generator

Create linear and radial CSS gradients with two colors, a custom angle and a preview. Copy the code or download a CSS file.

HEX RGB HSL CMYK color converter

Convert between HEX, RGB, HSL and CMYK. Preview the color, copy the values and download all four color representations.

You may also need

Useful tools from other categories. They are not included in the primary count.

Convert Excel to CSV

Convert an Excel XLSX sheet to CSV with sheet selection, delimiters, BOM and formula protection. Preview rows before downloading.

Convert CSV to Excel

Turn CSV or TSV into Excel XLSX with delimiter and encoding options. Preserve leading zeroes and formula-like text.