How we make this list: we compare pricing pages, product documentation and public user reviews. Ratings come from G2, Capterra or Trustpilot, with the date we checked them.
Key takeaways
- Keyword gap analysis compares your domain against competitors to find keywords they rank for that you do not, sorted into shared, missing, weak, and untapped groups.
- Semrush Keyword Gap is the feature everyone else copied, comparing up to five domains with the four-way split that makes prioritization possible.
- Ahrefs Content Gap offers the cleanest data of the three majors, with an index most practitioners trust for accuracy and flexible intersection filters.
- SE Ranking is the sensible mid-market pick, costing meaningfully less than the two leaders with white-label reporting for client work.
- No gap tool guarantees rankings: gaps show opportunity, but winning them needs content quality, links, and authority, not just a keyword list.
Quick comparison
| Tool | Best for | Starting price | Free plan |
|---|
 Semrush | Broad competitive SEO and PPC | $139 per month | Yes |
 Ahrefs | Backlink and keyword intelligence | $29 per month | No |
 SE Ranking | Sensible mid-market pick | $129 per month | No |
 Moz Pro | Accessible all-round suite | $49 per month | No |
 Search Atlas | Gap plus topical dominance | $99 per month | No |
 SpyFu | Budget competitor research | $39 per month | No |
 Similarweb | Traffic and audience intelligence | $199 per month | No |
 Serpstat | Budget gap analysis | $69 per month | No |
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#1Semrush
Best for: Broad competitive SEO and PPC4.4/5 on
G2 (4,035 reviews, checked Oct 2026)
Visit semrush.com
Starting price$139 per month
Free planYes
What we like- Semrush Keyword Gap is the feature everyone else copied, comparing up to five domains at once with every query sorted into shared, missing, weak, and untapped. The four-way split is the reason it is the standard: missing and weak are different problems, and a tool lumping them together gives a list you cannot prioritize. The SEO plan costs 139 dollars per month, or 117.33 dollars per month billed annually, with a limited free tier offering limited lookups per day.
Watch out for- It is one module of an expensive suite, and comparing five domains on the entry plan burns through daily limits fast. Backlink gap analysis covers 4 competitors in one comparison, with market relevance filtering but no published metric. Entry pricing suits agencies and in-house teams better than hobby bloggers.
#2Ahrefs
Best for: Backlink and keyword intelligence4.5/5 on
G2 (717 reviews, checked Oct 2026)
Visit ahrefs.com
Starting price$29 per month
Free planNo
What we like- Ahrefs Content Gap works at the keyword level despite the name, comparing your site to competitors to identify keywords they rank for that you do not, with the cleanest data of the three majors and an index most practitioners trust for accuracy. Intersection filters are more flexible than the competition, and the report adds traffic share, SERP features, difficulty, and intent to every keyword, turning a flat gap list into something sortable by commercial value. Starter costs 29 dollars per month, with full plans from 129 dollars per month for Lite.
Watch out for- There is no free tier worth planning around, since Webmaster Tools covers your own site only, and pricing is set for professionals with no monthly plan making casual use sensible. Lite adds a 1,000-credit monthly limit that other plans do not share in the same form. The interface is dense and the learning curve steeper than Moz.
#3SE Ranking
Best for: Sensible mid-market pick4.7/5 on
G2 (1,606 reviews, checked Oct 2026)
Visit seranking.com
Starting price$129 per month
Free planNo
What we like- SE Ranking offers a competent gap comparison inside a suite costing meaningfully less than the two leaders in effective value, with white-label reporting for client work. Core costs 129 dollars per month, or 103.20 dollars per month billed annually, tracking 2,000 keywords daily versus Ahrefs Lite 750 weekly at the same monthly price. It suits agencies and scaling teams wanting gap analysis plus rank tracking, audits, and reporting in one suite.
Watch out for- The index is smaller than Semrush or Ahrefs, which shows most in long-tail and non-English markets. Gap depth lags the leaders for very competitive niches, and backlink gap covers 5 competitors with Domain Trust and Page Trust filters but no outreach built in. Enterprise scale needs higher tiers.
#4Moz Pro
Best for: Accessible all-round suite4.3/5 on
G2 (608 reviews, checked Oct 2026)
Visit moz.com
Starting price$49 per month
Free planNo
What we like- Moz Pro offers an accessible all-round SEO suite with keyword gap analysis and intuitive scoring, suiting SMBs and growing in-house teams. Starter costs 49 dollars per month, with Standard at 99 dollars per month, and a 30-day trial lets teams evaluate before paying. Domain Authority is the metric many industries speak, and the interface is easier than Ahrefs or Semrush for beginners. Link Intersect covers 5 competitors with Domain Authority and Spam Score filters.
Watch out for- Gap data depth lags Semrush and Ahrefs, and the index is smaller for competitive analysis. Standard includes only 3 campaigns and 300 keywords, with extra campaigns and keyword blocks adding cost, reaching 139 dollars per month for a 5-site, 500-keyword freelancer setup in one comparison. Advanced practitioners may outgrow it.
Starting price$99 per month
Free planNo
What we like- Search Atlas Keyword Gap compares up to 6 domains, showing keywords in common, keyword opportunities, and unique keywords, plus content gaps and topical coverage measured by a Topical Dominance score from 0 to 100. Starter costs 99 dollars per month, or 79 dollars per month billed annually, and the platform runs competitor keyword analysis alongside keyword research, content, on-page, off-page, PPC, and technical SEO in one workspace. Report Builder turns data into white-label client reports on Pro and above.
Watch out for- The platform is newer than Semrush and Ahrefs, with a smaller practitioner community and fewer independent index comparisons. OTTO SEO automation pricing scales per site, from 99 dollars for one site to 49 dollars per site at 25 to 99 sites, adding cost for multi-site automation. Gap depth for very large indexes is less proven.
#6SpyFu
Best for: Budget competitor research4.6/5 on
G2 (518 reviews, checked Oct 2026)
Visit spyfu.com
Starting price$39 per month
Free planNo
What we like- SpyFu offers budget-friendly competitor keyword and PPC research, with historical keyword and ad insights showing what competitors ranked for and advertised over time. Basic costs 39 dollars per month, or 29 dollars per month billed annually, making it the cheapest paid gap tool on this list. It suits freelancers and early-stage teams wanting competitor keywords without suite prices.
Watch out for- The index is smaller than Semrush and Ahrefs, and gap analysis depth lags the leaders, with fewer sorting dimensions for commercial value. Historical data is the strength, not real-time gap freshness. Agencies needing white-label reporting and audits should pair it with another tool.
#7Similarweb
Best for: Traffic and audience intelligence4.4/5 on
G2 (1,236 reviews, checked Oct 2026)
Visit similarweb.com
Starting price$199 per month
Free planNo
What we like- Similarweb offers traffic and audience intelligence with channel-level content opportunities, going beyond keyword gaps into traffic sources, audience behavior, and competitive intelligence generally. Competitive Intelligence starts at 199 dollars per month, or 125 dollars per month billed annually in one comparison, and it suits enterprises and performance marketers needing the full competitive picture, not just keyword lists.
Watch out for- Enterprise pricing and an enterprise sales process make it the most expensive tool here, and gap analysis is one part of a broader intelligence purchase. Keyword-level gap depth lags dedicated SEO suites for practitioners wanting pure gap lists. Smaller teams get better value from SE Ranking or SpyFu.
#8Serpstat
Best for: Budget gap analysis4.6/5 on
G2 (464 reviews, checked Oct 2026)
Visit serpstat.com
Starting price$69 per month
Free planNo
What we like- Serpstat offers budget gap analysis with an Individual plan at 69 dollars per month, or 50 dollars per month billed annually, covering 5 projects and 10,000 rank position checks per month. It suits freelancers and small teams wanting gap analysis plus rank tracking at a mid price, with a Team plan at 100 dollars per month for heavier check volumes. The suite covers keyword research, audits, and backlink analysis alongside gaps.
Watch out for- The Individual check allowance covers only about 10,000 checks, so 500 keywords checked daily use roughly 15,000 checks per month, exceeding the plan and requiring Team. The index is smaller than Semrush and Ahrefs, and gap sorting dimensions lag the leaders. Non-English and long-tail coverage is thinner.
How we chose
We ranked tools on gap split quality, index size and accuracy, sorting dimensions, competitor counts per run, and published pricing. Tools earned credit for the four-way shared, missing, weak, and untapped split, traffic and intent data, flexible intersection filters, and white-label reporting. We excluded pure rank trackers without gap comparison, since domain comparison defines this category. Figures come from published pricing and 2026 comparison reporting, and readers should confirm current terms directly, since entry prices and credit limits change.
Start with your budget and depth needs: Semrush and Ahrefs suit serious SEO with the largest indexes, SE Ranking suits mid-market teams wanting value, and SpyFu and Serpstat suit budget-conscious freelancers. Next, check the gap split: tools lumping missing and weak together give lists you cannot prioritize, so prefer the four-way split. Then check competitor counts per run: Semrush compares 5 domains, Search Atlas 6, and backlink gap tools vary from 4 to 10 competitors, so match the count to your competitive set. Then check sorting dimensions: traffic share, difficulty, intent, and SERP features turn a flat list into a commercial priority queue. Finally, remember no tool guarantees rankings: gaps show opportunity, but winning them needs content quality, links, and authority, so budget for content production and outreach alongside the tool subscription.
Frequently asked questions
What is keyword gap analysis?
Keyword gap analysis compares your domain against competitors to find keywords they rank for that you do not, sorted into shared, missing, weak, and untapped groups. It reveals proven demand you are not capturing and prioritizes content opportunities.
What is the best keyword gap tool?
Semrush Keyword Gap is the standard with its four-way split and five-domain comparison, while Ahrefs Content Gap offers the cleanest data and most trusted index. SE Ranking is the sensible mid-market pick, and SpyFu suits budget-conscious teams.
How much do keyword gap tools cost?
From 29 dollars per month for Ahrefs Starter and 39 dollars for SpyFu Basic, to 49 dollars for Moz Starter, 69 dollars for Serpstat Individual, 99 dollars for Search Atlas Starter, 129 dollars for SE Ranking Core and Ahrefs Lite, 139 dollars for Semrush SEO, and 199 dollars for Similarweb Competitive Intelligence.
Can a keyword gap tool guarantee rankings?
No. Gap tools show opportunity, but rankings depend on content quality, links, authority, and search intent match. No tool can guarantee rankings, and any vendor claiming otherwise should be treated with skepticism.
What is the difference between missing and weak keywords?
Missing keywords are ones competitors rank for that you do not rank for at all, while weak keywords are ones you rank for poorly compared with competitors. They are different problems: missing needs new content, while weak needs improvement of existing content.
How many competitors should I compare?
Compare your closest 3 to 5 competitors for a focused gap list, since Semrush supports 5 domains and Search Atlas supports 6. More competitors add noise, while fewer miss opportunities, so start with direct rivals and expand only if gaps look thin.
Sources we checked (0)
Is your product missing or out of date?
We review this list regularly. Vendors can request a listing, send updated pricing or ask about featured placement.
Shihab Mia · Founder, Rankite
Shihab has 5+ years in B2B and SaaS SEO. He writes Rankite's software buying guides from pricing pages, documentation and public user reviews. More about Shihab.