We think there are many reasons to choose Total Validator, such as cross-platform support, DOM validation, and support for login forms. But our users say that these are probably the top three:
HTML Validators fall into two camps: The first, like the W3C's, use the official DTDs that define the standards. But these are severely limited by the DTD language. So they can't test all the rules of the standards, such as restrictions on the values of attributes.
The second camp are custom validators that use their own rules. But these often misinterpret the standards, or miss rules within the DTDs, or add in rules that actually don't exist in the standards. So although they tend to test more things, they are more likely to perform worse than DTD validators.
Total Validator is unique in that we test using the official DTDs to ensure that we're as good as any DTD validator, and then add in custom tests for everything that the DTDs can't cover. This ensures the best possible test against the standards.
Note that HTML5 doesn't have a DTD, but it's built on previous standards. So we've produced our own HTML5 DTDs using the previous ones to ensure we introduce the minimum of mistakes. Then we've added custom tests to cover the differences.
Using an accessibility tool on its own is not good enough. Conforming to standards also means strictly validated HTML, or accessibility technology may fail to properly read your site.
Every web professional knows that broken link checkers are essential, and CSS and spell checkers are difficult to find. But think of the time it takes to use each type of tool for each page on your site. Each tool will have its own way of working and produce its own type of report, and there's a lot to learn. Plus you'll need to run each of these tools every time you make a change, so that's a lot of overhead.
Total Validator provides all of these tools in one great package. You can check everything with with just one click, reducing the time to validate your site (or multiple sites) properly, minimising the costs of making changes.
Standards change, users requests extra features, and sometime bugs are found. We want to Total Validator to be the best, and we know you can't be the best by standing still.
That's why we were the first HTML5 validator, the first XHTML5 validator, the first HTML 5.1 validator, and probably the only up to date CSS 3 validator. That's why we issue regular updates, and that's why it's worth investing in using our tools rather than others.