Website accessibility monitoring tools, compared

Six tools that organisations shortlist when they need a website to be accessible and to stay that way: Askem, Siteimprove, Silktide, DubBot, Monsido and accessiBe. Compared on accessibility and content quality alone, because that is the obligation the law actually places on you.

Last updated August 2026 · Reviewed by the Askem accessibility team

What we compare, and what we leave out

Several tools here also sell SEO, site-speed monitoring or a content platform. Comparing those would tell you which vendor bundles the most, not which one keeps your site accessible. If you need an SEO platform, buy one. This page answers a single question: which of these will find the accessibility problems on your site, and help you clear them.

Not compared: SEO tools, including keyword research, rank tracking and backlinks
Not compared: Site speed and performance monitoring
Not compared: Content management, experience platforms and personalisation

Two different kinds of product

Monitoring tools

They crawl your published site, report what fails against WCAG, and leave you with a list to fix. Your actual pages change, and you can prove what was found and what was fixed.

Askem · Siteimprove · Silktide · DubBot · Monsido

Overlays

They add a widget that changes pages inside the visitor's browser. Your published code stays as it was, so anyone auditing it still finds the original problems.

accessiBe · UserWay · AudioEye

Capability comparison

Accessibility monitoring capabilities compared across Askem, Siteimprove, Silktide, DubBot, Monsido and accessiBe
Capability	Askem	Siteimprove	Silktide	DubBot	Monsido	accessiBe
Continuous site-wide WCAG scanning	✓ Yes	✓ Yes	✓ Yes	✓ Yes	✓ Yes	Partial Partial
Broken link detection	✓ Yes	✓ Yes	✓ Yes	✓ Yes	✓ Yes	— No
Readability and content quality	✓ Yes	✓ Yes	✓ Yes	✓ Yes	✓ Yes	— No
Page-level feedback from real users	✓ Yes	— No	— No	— No	— No	— No
EU data residency	✓ Yes	Partial Partial	Not published Not published	Not published Not published	Not published Not published	Not published Not published
Cost per montha 10,000-page site with more than 50,000 visits a month	€199	€2,530–5,050estimated	€1,440	Not published	€360–1,080estimated	€415
Approach	monitoring	monitoring	monitoring	monitoring	monitoring	overlay

Compiled from each vendor's public product and pricing pages, August 2026. "Not published" means the vendor does not state it publicly, not that the capability is missing. Tell us if anything here is out of date.

What these actually cost

Four of the six do not publish a price at all. That is the most frustrating part of buying one of these tools: you cannot build the business case until you have been through a sales call. Here is everything that can be known publicly, each figure with its source.

Published pricing and scaling model for Askem, Siteimprove, Silktide, DubBot, Monsido, accessiBe
Tool	Price published?	Per month for this site	Cheapest starting price	What it scales on
Askem	Yes, on their site	€199published	€199 / month	Per domain, with each extra domain at a small added cost. Not tiered by pages or by traffic, so the figure does not move as the site grows.
Siteimprove	No, quote only	€2,530–5,050*estimated	Not published	Quoted on pages monitored, modules licensed and contract length. Buyers report roughly €870 to €2,170 a month at 1,000 to 5,000 pages.Watch for: Priced per module, so accessibility, SEO, analytics and content governance each show up as a separate line on the quote.
Silktide	Public-sector framework only	€1,440published	€490 / month at 1,000 pages	By pages scanned. Published UK public-sector rates convert to about €880 a month at 5,000 pages, €1,440 at 10,000, €2,915 at 25,000 and €4,300 at 50,000.
DubBot	No, quote only	Not published	Not published	Quoted per institution, with discounts through purchasing consortia such as HESS. There are no published rates, no free plan and no reliable public benchmark, so the only way to get a number is to ask.
Monsido	No, quote only	€360–1,080*estimated	Not published	Quoted, usually inside a wider Acquia relationship. Third-party reporting puts it around €360 to €1,080 a month.
accessiBe	Yes, on their site	€415published	€51 / month up to 5,000 visits	By monthly traffic: about €155 a month up to 30,000 visits, €415 up to 100,000.Watch for: The cheapest tier stops at 5,000 visits a month. A site the size compared here sits on the €415 tier, and it is still an overlay.

Converted at €1 = £0.855 = $1.154, the rate on 10 August 2026. Annual figures divided by twelve. Checked August 2026. * Third-party estimate reported by buyers, not a figure the vendor publishes. Treat it as a range, not a quote.

One large site, priced six ways

Entry prices are hard to compare when vendors scale on different things: pages for one, traffic for another, modules for a third. So here is one realistic example at the size these tools are actually bought for, a public-sector site of 10,000 pages with more than 50,000 visits a month.

At this size Askem is the cheapest of the options that publish a price, and the gap widens as the site grows, because Askem is the only one here that does not charge by page count or by traffic. Below this size the answer changes: for a small site under 5,000 visits a month, accessiBe's €51 tier is cheaper than anything else on this page, even with everything an overlay does not do.

Askem

€199 / month

Published. Priced per domain, not by pages or traffic, so it does not move as the site grows.

Monsido

€360–1,080 / month*

Estimated. Quoted privately, usually inside an Acquia contract.

accessiBe

€415 / month

Published. This is the tier you need above 30,000 visits, and it is still an overlay, so your own site is unchanged.

Silktide

€1,440 / month

Published UK public-sector rate at 10,000 pages.

Siteimprove

€2,530–5,050 / month*

Estimated from what buyers report at 10,000 to 25,000 pages.

DubBot

Not published

No published rate and no reliable public benchmark. You would have to ask for a quote.

Converted at €1 = £0.855 = $1.154, the rate on 10 August 2026. Annual figures divided by twelve. * Third-party estimate, not vendor-published. Askem's figure is its published price for one domain. The others are list or benchmark figures and would be open to negotiation. Two of the six publish nothing at all, so "cheapest" here can only mean cheapest among those that do.

What actually decides this

Continuous site-wide WCAG scanning: A one-off audit is out of date the next time somebody publishes a page. You have to stay accessible, not pass once.
Broken link detection: Dead links are both an accessibility problem and the thing real visitors complain about most.
Readability and content quality: WCAG is also about whether people can understand your content, not only whether a screen reader can read it aloud.
Page-level feedback from real users: Automated scanning catches roughly a third of accessibility problems. People find the rest.
EU data residency: In European public-sector buying this is often a straight yes or no requirement, not a preference.

Compare a specific tool

Siteimprove alternatives →

The big enterprise platform. Broad, quoted rather than priced, and more than most teams need if accessibility is the actual obligation.

Silktide alternatives →

Strong disability simulations, bundled with SEO and site speed. The best of these for helping colleagues understand why accessibility matters.

DubBot alternatives →

Focused accessibility and content QA with custom rules, popular in North American higher education and government.

accessiBe alternatives →

An overlay rather than a monitoring tool, which makes it a different kind of product entirely. Read this one before you choose either.

Silktide vs Siteimprove →

The two platforms buyers compare most often, head to head on accessibility scope alone.

Accessibility monitoring: common questions

What is website accessibility monitoring?

Accessibility monitoring is the continuous automated checking of a website against WCAG, so problems are caught as content is published rather than discovered in an annual audit. It typically covers page structure, alt text, contrast, broken links and readability.

What is the best website accessibility tool?

There is no single best. Askem suits European organisations needing EU data residency and published pricing; Siteimprove suits enterprises wanting governance breadth; Silktide suits teams building internal understanding; DubBot suits North American higher education. Match the tool to the obligation you actually have.

What is the difference between a monitoring tool and an overlay?

A monitoring tool scans your published site and reports what to fix, so the underlying pages change. An overlay injects a widget that alters pages in the visitor's browser, leaving your published code unchanged. Only the first produces evidence you can show a regulator.

Can automated tools make a site fully accessible?

No, and be sceptical of any vendor who says otherwise. Automated testing reliably catches roughly a third of accessibility problems and gives you a dated, repeatable record that you are monitoring. People find the rest, which is why feedback from real visitors on real pages belongs alongside any scanner.

Which accessibility tools publish their pricing?

Among the tools compared here, Askem publishes pricing from €199 a month and accessiBe publishes subscription rates. Siteimprove, Silktide, DubBot and Monsido all quote instead. Published pricing lets you build an internal business case before booking a sales call.

See what Askem finds on your site. Book a 20-minute review.

Published pricing from €199/month
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