Keyword gap analysis tools, and a free method

A keyword gap analysis tool compares the search terms your site ranks for with those your competitors rank for, and lists the ones you are missing. Semrush's Keyword Gap and Ahrefs' Content Gap are the best known; Moz Pro, SE Ranking, Serpstat and Ubersuggest offer cheaper versions, and SpyFu does the same for paid search. They all work from each vendor's own keyword database, so the lists differ between tools.

The tool is the easy part. A raw report returns thousands of keywords, and the value comes from filtering them down to the few dozen worth a page. The competitor keyword research guide covers that process; this page compares the tools.

How we chose

Each tool had to offer a dedicated report that compares your domain with named competitors and isolates the keywords you lack. We checked each feature on the vendor's own help or product page on 4 October 2026 and recorded how many competitors it compares, because that limit shapes the analysis. Prices below were read from each vendor's own pricing page on 4 October 2026.

Keyword gap analysis tools compared

The tools

Semrush Keyword Gap

The most detailed report here. It compares up to five domains, subdomains, folders or exact URLs, and splits the results into tabs: Shared, Missing (all competitors rank, you do not), Weak (you rank below all of them), Strong, Untapped (at least one competitor ranks, you do not), Unique and All. It covers organic, paid and Google Shopping keywords.

Missing and Weak are where to start, because several rivals ranking for a term is better evidence of value than one. The SEO plan is $139 a month, or $117.33 billed annually, and the free plan allows 10 reports a day across Semrush's main tools. Semrush vs Ahrefs compares the two leaders in full.

Ahrefs Content Gap

Ahrefs' version lives under Competitive Analysis. You enter your site and up to 10 competitors, and it returns the organic keywords they rank for and you do not. Its strength is the quality of Ahrefs' keyword and link data around each result.

Lite is $129 a month on monthly billing for one user. Ahrefs' free Webmaster Tools only cover sites you own, so they do not help here.

Moz Pro Keyword Gap

Moz compares your domain, subdomain or subfolder with up to 3 competitors, using keywords ranking in the top 50. Its views are practical: Keywords to improve (a competitor outranks you and you sit in positions 2 to 20), New keyword opportunities, Winning keywords and All. A Traffic Lift figure estimates what overtaking a competitor would be worth.

Standard is $99 a month or $79 billed annually; a single-site Starter plan is listed at $49 without published limits, so check it includes the report.

SE Ranking

SE Ranking's Competitive Research tool shows a Missing Keywords column for each competitor, and a Competitors Comparison tab where you add up to two more domains to compare with yours. Core is $129 a month or $103.20 billed annually, with a 14 day trial and no card.

Limit. Three domains at once, yours included, is the tightest comparison here, shared with Serpstat.

Serpstat Keyword Gap

Serpstat renamed its "Compare domains" report to Keyword Gap and added a Missing column. It compares two or three domains across organic and paid results. Individual is $50 a month. The 7 day trial needs a card: Serpstat takes a $1 verification charge, refunds it, and renews automatically unless you cancel.

Ubersuggest

Ubersuggest's competitor report lists, for each rival, the keywords you share and the gaps, meaning terms they rank for and you do not. It is simpler than the others and limited by plan: the Individual plan covers 5 competitors and 1 project, at $16 a month on a yearly limited-time offer ($192 a year). A free account exists, but Ubersuggest does not spell out its limits.

SpyFu Kombat, for paid search

Kombat compares advertisers rather than organic rankings. It shows the keywords all listed competitors buy, those they buy and you do not ("Consider Buying"), and those you buy and they do not ("Potential Ad Waste"). Basic is $39 a month; the history-rich Pro + AI plan is $59 for the first month, then $119.

The free method

Without a paid tool you can still find most of the gap, by topic rather than by keyword.

1. List their pages. Open their sitemap (usually at /sitemap.xml) and copy the URLs into a sheet. Finding all pages on a website covers sites without one.
2. List yours the same way.
3. Mark the topics they cover and you do not. URL slugs usually name the topic.
4. Check the search results for each missing topic in a private window. If the competitor's page ranks on page one, it is a real gap.
5. Check Search Console for queries where you already appear on page two. They are close to what the paid tools call weak keywords, found free.

This misses keyword volumes and ranks, but it finds the topics, which is where most of the value is.

Our own product, Figo, is a weekly competitor monitor rather than a research tool, which is why it is not listed. It reports new pages competitors publish, not the terms you lack.

Which one to pick

• You want the fullest report and already pay for a suite: Semrush.
• You care about link data alongside the gap: Ahrefs.
• Small budget: Serpstat or Ubersuggest.
• You buy Google Ads against the same rivals: SpyFu Kombat.
• No budget: the sitemap method, then a free plan to confirm. The free Semrush alternatives page lists more.