Check Engine vs Semrush Site Audit
Semrush sells an index of the web with an audit tool attached. Check Engine sells the audit tool and nothing else. If Site Audit is the part of Semrush you actually open, you are renting the index to get at it, and the question on this page is whether that trade is worth $139 a month or more to you. For a lot of people it is.
What the subscription buys that a download cannot
The concessions come first because they settle the question for most readers. Six things Semrush gives you that Check Engine has no version of:
- Backlinks. Referring domains, anchor text, who links to a competitor and not to you. That comes from crawling the web continuously and keeping the result. Check Engine holds none of it and is not building any.
- Keyword research. Volume, difficulty, the gap between your coverage and someone else's. Same index, same reason. A tool without one that prints a monthly search volume is showing you a guess with a number on it.
- Rank tracking. Their pricing page puts "500 keywords to track daily" on the entry plan. Check Engine never looks at a search result page, so it has no idea where you sit on one.
- Trend lines for the whole site. Their technical SEO page describes tracking "how each issue category trends over time". That is the chart that shows a client the retainer bought something. Check Engine has no equivalent view.
- Crawling somewhere other than your desk. Audits scheduled daily, weekly or monthly run on their machines whether your laptop is open or shut, at 20,000 pages an audit on Pro and Guru and 100,000 on Business.
- More than one person. Seats, shared projects, dashboards, alerts.
Their knowledge base also says Site Audit can "check over 140+ website issues", against Check Engine's 99. A count is a weak measure of an audit. What decides its worth is the order the findings arrive in and what each one tells you to do. It is still a larger number, and writing around that would be its own kind of tell.
One further concession, which retires something this site has leaned on elsewhere. Semrush's Site Audit page now checks AI crawler access per bot, naming ChatGPT-User, OAI-SearchBot, Googlebot, Google-Extended, Perplexity-User, PerplexityBot, Claude-User and Claude-SearchBot. Check Engine checks the same crawlers. What it adds is the sorting: search crawlers on one side, training crawlers on the other, which is the distinction that decides whether a block in your robots.txt costs you citations or only costs a model some training data.
Severity is not a plan
Semrush groups findings into three tiers and its knowledge base gives the order as "Errors (most harmful to a website) - Warnings (harmful) - Notices (least harmful)". That says how bad each thing is. It does not say what to do on Tuesday morning.
The gap opens as soon as two findings land in the same tier. A noindex left on a
pricing page and 300 thin product descriptions are both errors. One is a two-minute change worth
more than everything else on the list; the other is a quarter of somebody's writing time. Check Engine
scores each finding on impact against effort and drops it into one of four phases: stop the
bleeding, quick wins, build, polish. Reach is compressed as well, so a trivial issue that
happens to appear on 4,000 pages does not outrank a serious one on the homepage. The report
opens as a sequence instead of a filter you have to operate.
The audit stays on your computer
Check Engine has no account, no sign-in and no telemetry. The crawl runs on your machine and each
run is written to ~/.docket/ as plain JSON you can diff, script against, or delete.
Five checks reach outside by default and --offline turns all five off;
the licence key is checked with the payment provider about once a day.
Two consequences that matter in practice. Auditing a prospect's site before a pitch is a quieter act on your own laptop than inside a vendor's project workspace. And re-running costs nothing, so a fix gets verified the moment it ships rather than saved up until a crawl is worth spending. Semrush's allowance is 100,000 pages a month on Pro, 300,000 on Guru and 1,000,000 on Business, and their knowledge base notes those reset on the 1st rather than rolling over.
Feature by feature
| Check Engine | Semrush Site Audit | |
|---|---|---|
| Billing | Paid once | $139–$299/mo, and Advanced by quote |
| Where the crawl runs | Your computer | Their cloud |
| Crawl allowance | Whatever your machine will do | 20,000–100,000 per audit, metered monthly |
| Checks | 99 | 140+ |
| Output | Four phases, impact against effort | Errors, warnings, notices |
| Backlink data | None | Yes |
| Keyword volume & difficulty | None | Yes |
| Rank tracking | No | 500 keywords daily on the entry plan |
| Trending over time | Each run kept locally as JSON | Charted by issue category |
| Seats | No | Yes |
| Reports with your own name and logo | Yes | Yes |
| AI crawler access | Per bot, split search from training | Per bot |
| Account required | None | Yes |
| Runs on | macOS on Apple silicon or Intel | Any browser |
The arithmetic, and why it flatters Check Engine
Semrush's pricing page lists the entry plan at $139 a month, or $117.33 a month billed annually. Paid monthly that is $1,668 in the first year and the same again in the second. Check Engine is $59 once (activation is a licence key you paste in once), which works out at roughly 2 weeks of the cheapest Semrush plan.
Then take the flattery back out. That $139 is not the price of a site audit. It is the price of keyword research, rank tracking and a backlink index, with an audit included. If you use those three, cancelling to save on the audit saves nothing, because the rest of the platform still costs $139. The comparison only runs one way: when Site Audit is the tool you open and the remainder is shelfware.
One caveat we are not going to paper over. Their pricing page currently sells SEO, Starter, Pro+ and Advanced, and Advanced is custom: you ask for a demo rather than see a price. Their knowledge base documents crawl limits under Pro, Guru and Business, and says that Semrush One Starter includes the Pro toolkit, Pro+ the Guru one and Advanced the Business one. It does not name the $139 SEO plan, so we have not guessed which allowance that one carries. Read the limits on the plan in front of you rather than trusting the row above.
Reasons to buy Semrush instead
Check Engine is the wrong purchase, and a cheap wrong purchase is still wrong, if any of this is your week:
- You need to know who links to a competitor.
- You need search volume, keyword difficulty or a content gap analysis.
- You track positions for a keyword list and report on the movement.
- Two or more people have to open the same results, or the report has to carry a client's branding.
- Audits have to run on a schedule whether or not your machine is awake.
- Somebody wants a twelve-month trend line for a board deck.
- You are on Linux, where only the command-line build runs.
- Your crawls run to hundreds of thousands of URLs.
Two of those and it is not a close call. There is no version of this page where Check Engine wins that argument on price.
Who each one is for
Semrush suits people for whom search is the job rather than a Thursday afternoon: agencies pitching on keyword opportunity, in-house SEO teams reporting upward, anyone whose work needs the index behind it.
Check Engine suits people who need the audit itself, in order, on hardware they control, at a price that stops. Freelancers, marketers who own the website alongside four other responsibilities, and agencies auditing prospects who have not signed anything yet.
Running both is a normal answer rather than a fence-sit. The platform answers where you stand; the local tool answers what to change next.
Checked 19 October 2026. The factual claims about this product were read from its own pages on that date: the entry plan is listed at $139/mo, or $117.33/mo billed annually; Starter is $199/mo and Pro+ is $299/mo, and the Advanced plan above them is custom, reached by a demo request; the entry plan lists "500 keywords to track daily" (source); Site Audit can "check over 140+ website issues", ordered "Errors (most harmful to a website) - Warnings (harmful) - Notices (least harmful)" (source); the crawl allowance is 20,000 pages per audit on Pro and Guru and 100,000 on Business, against 100,000 / 300,000 / 1,000,000 pages a month, resetting on the 1st rather than rolling over; the same article says Semrush One Starter includes the Pro SEO Toolkit, Pro+ the Guru one and Advanced the Business one (the address this claim was first read at, kb/338, now redirects here) (source); AI crawler access is checked per bot, naming ChatGPT-User, OAI-SearchBot, Googlebot, Google-Extended, Perplexity-User, PerplexityBot, Claude-User and Claude-SearchBot (source); audits can be scheduled daily, weekly or monthly, with white-label reporting and tracking of "how each issue category trends over time" (source). Products change and pricing changes; if something here has gone out of date, tell us and it will be corrected. Everything else on this page is a comparison of approach, not a claim about their roadmap.
Check Engine is a one-time purchase for Mac and Windows: no account, no crawl credits, and the crawl runs
on your machine. Five optional checks fetch data it cannot produce alone; --offline
turns all five off.
$59once
For Macs with Apple silicon or Intel, macOS 12 or later, and 64-bit Windows
Priced in US dollars. Checkout shows your currency and any local tax.
On a Mac? Get the Mac version.
On your phone?
Launch price: $29.50 once, through 30 November. From 1 December: $59. Buy applies the code FOUNDINGDOCKET for you; if the checkout shows $59, enter it under ‘Have a discount code?’.
Screaming Frog is $279 a year. Ahrefs plans with Site Audit run $129–$449 a month. Check Engine is $59 once. Screaming Frog’s price read 4 November 2026, Ahrefs’ 9 November 2026.
30 days, no conditions, no questions asked. Refund policy
Intel Mac? Get the Intel version
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Common questions
Is Check Engine a Semrush alternative?
For the site audit, yes. For the rest of Semrush, no. Keyword volumes, backlink data and rank tracking come from an index of the web that Check Engine has no equivalent of and will not be building. Keep Semrush if you use those; Check Engine covers the audit for a one-time price.
How much cheaper is Check Engine than Semrush?
Semrush's pricing page lists its entry plan at $139 a month, or $117.33 a month billed annually, which is $1,668 in a year paid monthly. Check Engine is $59 paid once, about 2 weeks of that plan. The saving is only real if the site audit is the part of Semrush you use.
Does Check Engine have crawl limits like Semrush?
Not monthly ones. Semrush's knowledge base lists 20,000 pages per audit on Pro and Guru and 100,000 on Business, drawn against 100,000 to 1,000,000 pages a month depending on plan, resetting on the 1st. Check Engine crawls on your computer, so the bounds are the page and depth caps you set, and re-running an audit costs nothing.
Does Check Engine check AI crawler access like Semrush?
Both do, so this is not a reason to switch either way. Semrush's Site Audit page names ChatGPT-User, OAI-SearchBot, Google-Extended, Perplexity-User, PerplexityBot, Claude-User and Claude-SearchBot among the bots it checks. Check Engine checks the same crawlers and separates search crawlers from training crawlers such as GPTBot, because blocking one of those costs you citations and blocking the other does not.