Best Free SEO Audit Tools in 2026, Compared on Price

The best free SEO audit tools in 2026 are Ahrefs Webmaster Tools, Semrush's free Site Audit, SEOptimer, AIOSEO, Moz Pro, and DidYouSEO — but "free" means something different at every single one of them, and that difference is usually where people get surprised at checkout.

Some of these are free only for your own verified site. Some are free for a single one-off report but charge for anything recurring. Some call themselves free and then gate the actual audit results behind a signup wall. This is an honest comparison of what's really free, where the paid plan actually starts, and what each tool is genuinely best at — including where DidYouSEO fits, without pretending it's the only option worth using.

Best free SEO audit tools at a glance

Ahrefs Webmaster Tools

Ahrefs Webmaster Tools is genuinely free, not a trial — but the catch is real: it only works for domains you verify ownership of. You get a real site audit (100+ technical checks) and your own backlink profile, but you can't point it at a competitor's site to see what they're doing. If all you need is your own site's technical health, this is one of the most generous free tiers on this list. If you need to research anyone else's site, it can't help you.

Semrush's free Site Audit

Semrush offers a genuinely free site audit tool with no signup required for a basic check — useful for a quick, no-commitment scan. Where it changes is anything ongoing: ongoing tracked audits, historical trend data, and Semrush's full toolkit (keyword research, competitor analysis) live behind the Pro plan, which runs close to $140/month. Semrush is a genuinely deep platform if you need everything it does — the free audit is a taste of a much bigger, much more expensive tool. See DidYouSEO vs Semrush for a fuller breakdown of where the two differ beyond the audit itself.

SEOptimer

SEOptimer's free tier gets you a one-off audit report — useful for a single check, less useful if you want to track a site over time or run audits across multiple client sites without paying. Its paid plans ($29-$59/month) are priced for agencies that want white-label reporting without committing to a full enterprise platform, and that's genuinely where it's strongest: lightweight, branded, client-facing reports.

AIOSEO

AIOSEO is a different category from the rest of this list — it's a WordPress plugin, not a standalone audit platform, so it lives inside your WordPress editor rather than scanning a URL from outside. The free version gives real on-page guidance (title tags, readability, basic checks) as you write, but it's not a full technical site crawl the way the others on this list are. If your whole site is WordPress and you want SEO guidance baked into the writing process itself, this is a different, complementary tool rather than a direct substitute for a full audit.

Moz Pro

Moz Pro doesn't have a permanent free tier at all — just a 7-day trial with full access, after which plans start around $49/month (promotional pricing; standard list pricing runs higher across its four tiers). Moz's real strength is its link-metrics ecosystem (Domain Authority, its own backlink index), which is genuinely useful if you're already using Moz elsewhere — but if you're specifically looking for something free to use ongoing, Moz isn't built for that.

DidYouSEO

Full disclosure: we built this one. DidYouSEO's free plan includes 3 full site audits and access to all 29 free tools (schema checker, meta tags, Core Web Vitals, hreflang, and more) with no credit card required — not a one-off report, a real recurring allowance. Paid plans start at $19/month for unlimited audits and light competitor tracking, scaling to $49/month for agencies managing multiple client sites — see the full pricing breakdown.

Where it's genuinely different from the others on this list: AI-visibility tracking (whether ChatGPT, Gemini, and Perplexity mention your brand) ships as part of the same audit, not a separate add-on — which matters more every month as AI answer engines send a growing share of research-stage traffic. It's not the deepest platform here — Semrush and Ahrefs both have far more mature keyword and competitor research tools if that's specifically what you need — but on price-to-features for a solo founder or small agency, it's built to compete directly with tools charging 3-5x more for a comparable free-tier audit.

How to actually choose between them

If you only need your own site's data and nothing else: Ahrefs Webmaster Tools is hard to beat — it's free indefinitely, not a trial.

If you're an agency doing branded client reports: SEOptimer's paid tier or DidYouSEO's Growth plan both fit — compare what each includes per client before deciding, since pricing structures differ (per-seat vs. per-site).

If you're on WordPress and want SEO guidance while writing: AIOSEO's free plugin tier is a genuinely different, complementary tool — not a replacement for an external audit.

If AI visibility matters to your business (anyone selling to a research-heavy buyer, which is most B2B and most considered purchases now): DidYouSEO is the only tool on this list that checks it in the same audit, not as a bolt-on.

If budget is the deciding factor and you need more than a one-off report: DidYouSEO's free plan is the only one here offering recurring full audits with zero cost and no card, rather than a single report or a time-limited trial.

FAQ

What is the best completely free SEO audit tool? Ahrefs Webmaster Tools is the most generously free option with no time limit, but only for domains you own — it can't research competitor sites. For a free tool that also does recurring audits and competitor comparisons, DidYouSEO's free plan is the closest fit.

Do any of these tools have a real free plan, or are they all trials? Ahrefs Webmaster Tools and DidYouSEO both offer permanent free tiers (not time-limited trials). Semrush's audit tool is free with no signup but limited to a single scan. Moz Pro has no free tier at all, only a 7-day trial.

Which free SEO audit tool is best for agencies? SEOptimer is built specifically around agency-style branded client reporting at a lower price point than Semrush or Ahrefs. DidYouSEO's paid tiers also include bulk scanning and competitor tracking aimed at the same use case, at a lower starting price.

Does any free SEO tool also check AI search visibility? DidYouSEO is the only tool on this list that includes AI-visibility tracking (checking whether ChatGPT, Gemini, and Perplexity mention your brand) as part of its standard audit rather than a separate paid add-on.

Try the one with the most generous recurring free plan

Every tool on this list is worth knowing about for different reasons — but if you want a genuinely free, recurring audit (not a single report or a time-limited trial) that also checks whether AI assistants know your brand exists, run a free audit on DidYouSEO and see how it compares on your own site.