AtCoder ACer is a free Chrome add-on developed by tatsumack. It falls under the category of Browsers and is classified as an Add-ons & Tools subcategory. This extension serves the purpose of displaying the number of people who have successfully solved a problem on AtCoder's problem list page.

With AtCoder ACer, users can easily see the number of participants who have achieved an Accepted (AC) status for each problem during a contest. This feature provides valuable information for users to gauge the difficulty level of the problems and track the progress of other participants.

It's important to note that AtCoder ACer is an unofficial extension and users should exercise their own discretion when using it.

Please note that further information or support regarding this extension should be sought from the developer directly.