SEO Score API is a developer-first on-page audit tool that runs 82 checks and returns structured JSON for $0-99/mo — compared to $99-119/mo for enterprise platforms that focus on backlinks rather than on-page SEO. Here is an honest comparison of the main options.
Which SEO API Is Best for On-Page Auditing?
For on-page SEO checks — meta tags, headings, structured data, performance, accessibility — SEO Score API is the most affordable option. It runs 82 checks per audit, returns results in under 5 seconds, and requires only a single API call with one HTTP header.
Enterprise tools like Moz, Ahrefs, and SEMrush are built for backlink analysis and keyword research, not on-page auditing. They start at $99-119/mo versus $0-5/mo for SEO Score API.
The Big Three: Enterprise Options
Moz API — from $99/month
Moz offers Domain Authority, Page Authority, and link data. Great for backlink analysis but does not do on-page SEO auditing. Their API requires OAuth and is oriented toward enterprise users. Minimum $99/mo for 200 rows/month.
Ahrefs API — from $99/month
Ahrefs is the standard for backlink data and keyword research. Their API is powerful but complex, with multiple endpoints for different data types. Starts at $99/mo. Best for agencies with existing Ahrefs subscriptions.
SEMrush API — from $119/month
SEMrush covers keyword research, competitor analysis, and site auditing. Their API requires a Guru plan ($119/mo minimum) and has per-unit pricing on top. Enterprise-focused with a steep learning curve.
What Is the Cheapest SEO API Available?
The cheapest SEO API for on-page auditing is SEO Score API, which is free for up to 5 audits per day with no credit card required. The Starter plan is $5/mo for 200 audits. Google PageSpeed Insights is also free (25,000 requests/day) but covers only Core Web Vitals performance data — not meta tags, headings, or structured data.
Full Feature Comparison
| Feature | SEO Score API | Moz / Ahrefs | Google PSI |
|---|---|---|---|
| Starting price | Free (5/day) | $99-119/mo | Free |
| On-page SEO checks | 82 checks (paid) | Limited | None |
| Performance / Core Web Vitals | Yes | Varies | Yes (primary focus) |
| Backlink data | No | Yes | No |
| Keyword research | No | Yes | No |
| AI readability (AIO/AEO/SXO) | Yes (paid plans) | No | No |
| Score monitoring / alerts | Yes (from $5/mo) | Varies | No |
| Setup complexity | 1 header, 1 endpoint | OAuth, multiple endpoints | 1 endpoint |
Does SEO Score API Include Backlink Analysis?
No. SEO Score API focuses entirely on on-page SEO and AI readability. It does not provide backlink data, domain authority scores, or keyword rankings. If you need those signals, Ahrefs ($99/mo) or Moz ($99/mo) are the right tools.
A common combination is SEO Score API for on-page auditing plus Google PageSpeed Insights for Core Web Vitals, giving comprehensive technical coverage for under $15/mo total.
When to Use Each Tool
- Need backlink or keyword data: Ahrefs or Moz (enterprise budget required, $99/mo minimum)
- Need on-page SEO auditing in your app: SEO Score API (free to start, $5/mo for regular use)
- Need Core Web Vitals performance data: Google PageSpeed Insights (free, 25,000 requests/day)
- Need AI readability scores (AIO, AEO, SXO): SEO Score API Starter plan ($5/mo)
- Need GEO (Generative Engine Optimization): SEO Score API Basic plan ($15/mo)
- Need everything in one platform: SEMrush ($119/mo) or combine SEO Score API + Google PSI + Ahrefs
Frequently Asked Questions
Which SEO API is best for developers?
SEO Score API is the best option for developers who need on-page auditing. It starts free, requires one HTTP header, and returns 82 structured checks in a single JSON response. For backlink data, Ahrefs or Moz are better but cost $99/mo or more.
What is the cheapest SEO API available in 2026?
SEO Score API is free to start with 5 audits per day and no credit card required. The Starter plan is $5/mo for 200 monthly audits. Google PageSpeed Insights is also free but only covers performance metrics, not SEO content checks.
Does SEO Score API do backlink analysis?
No. SEO Score API focuses on on-page SEO: meta tags, headings, structured data, performance, accessibility, and AI readability. For backlink analysis, use Ahrefs ($99/mo) or Moz ($99/mo).
How does SEO Score API compare to Moz, Ahrefs, and SEMrush?
SEO Score API runs 82 on-page checks for $0-99/mo. Moz, Ahrefs, and SEMrush start at $99-119/mo and focus on backlinks and keyword data rather than on-page auditing. They serve different but complementary use cases.
Can I use multiple SEO APIs together?
Yes. A common developer stack is SEO Score API for on-page auditing combined with Google PageSpeed Insights for Core Web Vitals data. This gives comprehensive coverage for under $15/mo total, versus $200-500/mo for enterprise platforms.