Can a competitor report me for an inaccessible website?

A competitor cannot report your site, but can send something that arrives faster

Yes, it can, and in Germany this route is even faster than going to the market surveillance authority. There is no European system where a competitor files an official complaint directly with a market surveillance authority and that authority then imposes a sanction at the competitor's request — oversight of European Accessibility Act obligations lies with a designated authority per country, not among market parties themselves. What does exist, particularly in Germany, is the competition law route: a competitor or interest association can send an Abmahnung, a warning letter stating that a website does not comply with the requirements of the Barrierefreiheitsstärkungsgesetz and often requesting a statement, compensation and cessation of the alleged breach. This route operates via competition law, separate from oversight by the Marktüberwachungsstelle der Länder für die Barrierefreiheit (MLBF) in Magdeburg, and can arrive at your door faster than a letter from a market surveillance authority. What an Abmahnung for accessibility entails precisely and who can send it is further detailed on that page.

In other countries it works differently. The Netherlands does not have that competition law instrument in this form in the same way; here oversight operates through the ACM, which can also initiate investigations independently without a complaint being received — how this works is described on the page about investigation following an anonymous tip. If you supply in multiple EU countries, you may be subject to multiple regimes at the same time, which is further explained on the page about oversight when supplying in multiple EU countries.

Where this difference comes from

The European Accessibility Act, Directive (EU) 2019/882, requires each member state to establish market surveillance, but leaves the implementation to the member states. Germany has implemented this in the Barrierefreiheitsstärkungsgesetz (BFSG), with the MLBF as the market surveillance authority, while the existing German competition law on unfair competition continues to apply — and an inaccessible website can under certain circumstances be considered as such, making the Abmahnung route possible. In the Netherlands, the ACM is designated as the market surveillance authority, as described in the ACM's publication on website and app accessibility, without a comparable competition law alternative route for competitors.