103 free tools for SEO, images, and security

Professional-grade utilities, free forever. No signup, no watermarks. Fair-use limits keep them fast for everyone.

Checkers

24 tools

Redirect Checker

Trace the full redirect path of any link, hop by hop, with status codes and timing.

SSL Checker

Check any SSL certificate: expiry countdown, issuer, trust status and covered domains.

Bot User-Agent Lookup

Paste a user agent and see if it is a bot, which crawler it is, and what it claims to be.

Security Headers Checker

Grade any site A+ to F on its HTTP security headers, with a fix for every gap.

Meta Tag & OG Checker

Every head tag in source order, duplicate and conflicting tags, the real image size, and a separate preview per platform.

Robots.txt Tester & Generator

Test any robots.txt against real crawlers, or generate one with AI-bot blocking presets.

DNS Lookup & WHOIS

Look up any domain: DNS records, WHOIS registration, expiry and propagation checks.

Website Safety Checker

Transparent URL risk report: per-source results, coverage counts and lookalike-domain checks.

DMARC, SPF & DKIM Checker

Exact SPF traces, RFC 9989 DMARC Tree Walk, real DKIM key parsing and a merge-safe SPF generator.

Schema Markup Validator

Strict JSON-LD validation with typed rules and dated Google feature profiles.

Broken Link Checker

Scan any page for dead links: every 404, timeout and server error, color-coded.

Page Speed Checker

Real Core Web Vitals and a performance score for any URL, with prioritized fixes.

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HTTP Status & Header Viewer

The status code, final URL, response time and every response header of any URL.

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Sitemap Checker

Fetch an existing sitemap.xml, list its URLs and flag every one that does not answer 200.

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Hreflang & Canonical Checker

Read the canonical and every hreflang tag of a page and check they agree with the URL.

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WordPress Theme & Plugin Detector

See which theme and which plugins a WordPress site runs, from its public HTML.

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DNS Propagation Checker

Compare what two public resolvers answer for a record, and whether your change shows yet.

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Is It Down?

One request from our server: is the site up for everyone, or just not for you?

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Mixed Content Checker

Find every http:// image, script, style and iframe still loaded on an https:// page.

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Image Alt Text Checker

List every image on a page with its alt text, and flag the ones missing one.

More checkers

MX Lookup The mail servers of any domain, in priority order.
Nameserver Lookup Which nameservers a domain delegates to.
TXT Record Lookup Every TXT record of a domain: SPF, verification tokens and more.
Reverse DNS Lookup The hostname behind an IP address.

Generators

19 tools

Password Generator

Cryptographically secure passwords and passphrases, with entropy math and breach checks.

QR Code Generator

QR codes for links, WiFi, vCards and more. Custom colors, logos, SVG export, no expiry.

Favicon Generator

Real favicon.ico, PNGs, SVG, maskable PWA icons and a valid manifest, packaged as one ZIP.

Maskable Icon Generator

PWA and Android adaptive icons with the 40% safe zone handled, previewed under a real mask.

Invoice Generator

Create a professional invoice in your browser and download it as a PDF. No signup.

WordPress robots.txt Generator

Build a correct WordPress robots.txt with AI-bot blocking presets, without the classic mistakes.

XML Sitemap Generator

Crawl your site and download a ready-to-submit sitemap.xml, with robots.txt respected.

llms.txt Generator

Create a spec-correct llms.txt so AI assistants understand your site, and check any domain.

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.htaccess Redirect Generator

Correct 301 and 302 rules for Apache, one URL or a whole list, plus the WordPress defaults.

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WordPress Salts Generator

Fresh AUTH_KEY, SECURE_AUTH_KEY and the other six wp-config.php secrets, generated in your browser.

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OG Image Generator

A 1200x630 Open Graph image from a title, a line of text and your colors. Download as PNG.

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Slug Generator

Turn any title into a clean URL slug: accents transliterated, stop words optional.

More generators

Passphrase Generator Word-based passphrases you can actually type.
PIN Generator Random numeric PINs of any length.
Password Strength Checker Entropy, crack-time estimate and a breach check, all in your browser.
Bulk QR Code Generator Many QR codes from a list, as one ZIP.
vCard QR Code Generator A contact card people scan straight into their phone.
WiFi QR Code Generator Guests join your network with one scan.
Estimate Generator A quote or estimate PDF with the same layout as the invoice.

Image Tools

20 tools

Image Compressor

Compress JPEG, PNG and WebP right in your browser. Nothing is uploaded anywhere.

WebP & AVIF Converter

Real WASM WebP and AVIF encoding in your browser: verified output, lossless mode, ZIP.

Image Converter

Convert between JPG, PNG, WebP and more, in bulk, right in your browser. No uploads.

Image Resizer

Resize images by pixels, percent or presets for WordPress and social. Nothing uploaded.

More image tools

Compress JPEG Real MozJPEG encoding with a quality slider.
Compress Image to 100 KB Hit a 100 KB target for forms and uploads.
Compress Image to 1 MB Hit a 1 MB target without visible loss.
Reduce Image Size Shrink the file by resizing and re-encoding together.
HEIC to JPG iPhone photos to JPG, in the browser.
JPG to PNG Lossless PNG from any JPG.
JPG to WebP Smaller WebP files from JPG photos.
PNG to JPG Flatten PNG to JPG with a matte color.
PNG to WebP PNG graphics to WebP, transparency kept.
WebP to PNG Back to PNG for tools that cannot read WebP.
Image to AVIF The smallest modern format, encoded in your browser.
Resize Images for WordPress Featured image and Open Graph sizes in one pass.
Instagram Image Resizer Square, portrait and story sizes.
YouTube Thumbnail Resizer 1280x720 thumbnails under the 2 MB limit.
Image to Base64 A data URI for any image file.
Base64 to Image Preview and download an image from a data URI.

Developer

12 tools

JSON Formatter & Validator

Format, validate, repair and explore JSON with exact error positions and a tree view.

Base64 Encoder & Decoder

Encode and decode Base64 text and files both ways, with data URIs and image preview.

Color Picker & Converter

Pick any color and convert HEX, RGB and HSL, with shades, contrast and harmonies.

New

URL & HTML Entity Encoder

Percent-encode URLs and components, or escape and unescape HTML entities, both ways.

More developer

JSON Minifier Strip whitespace, keep it valid.
JSON Tree Viewer Fold and search a large JSON document.
Base64 Validator A strict verdict on any Base64 payload.
HEX to RGB Hex colors to RGB and back.
RGB to HEX RGB values to a hex code.
HSL to HEX Hue, saturation and lightness to hex.
OKLCH Color Picker Perceptual colors for modern CSS.
Color Contrast Checker WCAG contrast ratios for text and background pairs.

Calculators

16 tools

Amazon Commission Calculator

Project your Amazon Associates earnings by category, price and traffic, with EPC math.

Profit Margin Calculator

Cost and price in, profit, margin and markup out, with fees, quantity and health hints.

Marketplace Fee Calculator

See what eBay, Etsy and PayPal really take from a sale, itemized, with true net profit.

ROI Calculator

Simple and marketing ROI with annualized returns, break-even and sensitivity checks.

Ad Metrics Calculator

CPM, CPC, CTR, CPA and conversion rate from your campaign numbers, with max-bid math.

More calculators

Break-Even Calculator Units and revenue needed to cover fixed costs.
Markup Calculator Markup from cost and price, or price from markup.
Selling Price Calculator The price that hits a target margin after fees.
eBay Fee Calculator Final value and payment fees on an eBay sale.
Etsy Fee Calculator Listing, transaction and processing fees on Etsy.
PayPal Fee Calculator What PayPal keeps, and what to charge to net a figure.
ROAS Calculator Return on ad spend and the break-even ROAS for your margin.
Annualized ROI Calculator Compare returns over different holding periods.
CPA Calculator Cost per acquisition from spend and conversions.
CPM Calculator Cost per thousand impressions, any way round.
CTR Calculator Click-through rate from clicks and impressions.

Text Tools

10 tools

Word & Character Counter

Live word and character counts with reading time, platform limits and keyword density.

Readability Checker

Flesch, Gunning Fog and grade-level scores with the exact sentences that need fixing.

More text tools

Character Counter Characters with and without spaces, live.
Sentence Counter Sentences, average length and the longest ones.
Paragraph Counter Paragraphs and words per paragraph.
Reading Time Calculator How long a text takes to read at real speeds.
Keyword Density Checker How often each word and phrase appears.
Unicode Character Counter Code points, grapheme clusters and bytes.
Instagram Caption Counter Stay inside the caption and hashtag limits.
X Character Counter The 280 limit counted the way X counts it.

Builders

1 tool

UTM Link Builder

Build tracked campaign URLs with presets for email, ads and social, plus naming rules.

Previews

1 tool

SERP Snippet Preview

Simulate your title and meta description in Google, with real wrapping and rewrite-risk checks.

Free tools check once. DevDome watches always.

These tools answer a question right now. DevDome Analytics and Site Health keep answering it around the clock, on autopilot, for your whole site, with bots split out of every number.

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