If you choose a backlink research tool, you need the data access and history required for the analysis your team performs. OppAlerts publishes this page and sells one of the products on it. Nothing here ranks index sizes. No index was measured for this research, and the vendors report crawl volume in units that do not convert.
What can be compared is how each product charges for access to link data, how much history it keeps, and what it lets you do once you have the data.
Three different meters
Crawl credits. Ahrefs sells 100,000, 500,000 and 1,500,000 crawl credits at $129, $249 and $449 a month. History runs 6 months, 2 years, 5 years, or unlimited at Enterprise. API and MCP come on every plan including the cheapest. One user included, extras at $40, $60 or $80 a month.
Analyzable backlinks. Majestic sells rows and not credits: 1 million, 20 million and 100 million AnalysisResUnits across its tiers. Its Fresh Index can be checked several times a day and sits separately from the historic index. It positions itself for audit and prospecting across a small group of sites. If your requirement is analyzing large volumes of link rows, this is the most direct purchase in the category.
Bundled inside a platform. Semrush at $139 to $549 a month, SE Ranking at $129 and $279, and Serpstat from $50 all include backlink research next to keyword tracking and site auditing. Serpstat counts daily searches for sites, keywords and links at 100, 500, 1,000 and 5,000, so heavy link research draws down the same allowance as your keyword research.
Those three meters answer different questions. Credits suit periodic deep analysis of a few domains. Row allowances suit bulk export and your own processing. A platform allowance suits a team doing a little of everything.
History is the part buyers underbuy
A current backlink profile tells you where a site stands. History tells you which way it is going, and when you are deciding whether to chase a placement, direction is the more useful judgment.
Ahrefs sells history openly by plan: 6 months, 2 years, 5 years. Majestic splits fresh from historic. Several platform products state no retention period at all on the pages read, so ask what happens to your historical data if you downgrade.
OppAlerts reports PageRank history, with monthly link-graph measurements for a host, its www variant and its domain. Observations exist from 2017 and charts are drawn from January 2020. It measures something different from a backlink count. It describes a site's position in the link graph across a run of months instead of listing the links. You use it to decide whether a prospect has been gaining or losing standing before you invest in the relationship.
What you can do with the data
Here is where the products separate, because the analysis is rarely the point.
Link gap analysis exists in several of them, including Semrush, Ahrefs and OppAlerts. The operation is the same everywhere: enter your site and your competitors' sites, get back the sites linking to them and not to you. What differs is what happens next.
Prospecting from link data is where Ahrefs Brand Radar and OppAlerts both go further. Brand Radar advertises web mention tracking and link prospecting alongside the index, so a team already paying for Ahrefs may not need a separate prospecting tool at all.
Contact details for the sites you find is the step most link tools hand off to another subscription. OppAlerts Site Info returns the contact pages, emails, phone numbers and social profiles a site publishes, so a link gap result becomes something you can act on without a contact database. Those details are as published and nothing tests whether they still work.
Opportunity type filtering only exists in the OppAlerts Prospect Index, searched by meaning and by keyword. Filter to guest contribution pages, resource lists, expert roundups, podcasts, industry directories, award programs and speaking submissions. It answers where a link could come from, not only where your competitors got theirs.
Where OppAlerts does not compete
It publishes no crawl figure comparable to Ahrefs or Majestic, and this page claims nothing about relative index size. It has no site audit. Its API and MCP server are read-only, where Ahrefs provides both on every plan and Semrush, SE Ranking and Serpstat provide one or both.
For raw link analysis at volume, Majestic and Ahrefs are the specialists. If auditing link profiles is the job, buy one of them.
Shortlisting
| If your deciding requirement is | Shortlist |
|---|---|
| Analyzing large volumes of link rows | Majestic |
| Crawl depth with multi-year history | Ahrefs |
| API or MCP on the cheapest plan | Ahrefs |
| Link data inside a full SEO platform | Semrush, SE Ranking or Serpstat |
| Lowest entry price | Serpstat at $50/mo |
| A large team with no per-user charges | Serpstat or OppAlerts |
| A site's link-graph trend across years | OppAlerts PageRank history |
| Link gap results with contact details attached | OppAlerts |
| Finding link opportunities by type | OppAlerts, or Ahrefs Brand Radar |
Ask every vendor the same three questions. What does the meter count? How much history does the plan keep? What happens to that history if you downgrade? How competitor selection affects a backlink gap report covers the analysis itself.
Before committing to a plan, test a representative link analysis and its output. Check the required volume and history against that task.
See also PageRank history and PRoT and link prospecting tools.