How can I build a mobile-friendly app that blocks spoilers?

A browser extension could inspect the page’s HTML, find visible text, and replace or hide phrases that match a keyword list. For more advanced detection, the text could be sent to an AI model to classify possible spoilers, but that adds cost, latency, privacy concerns, and complexity. Allowing users to provide their own model or API configuration could reduce your service costs, but it would still be a fairly advanced feature.

A normal website generally can’t control or modify pages that are open in another browser tab. If the goal is to hide content across social media and other sites, you’d need something with browser-level access, such as an extension, a customized mobile browser, or possibly a filtering app with operating-system permissions. A standalone site could only filter text that users paste into it or content loaded inside that site.

The first design question is how you define a spoiler and where the tool should work. Filtering the entire internet is extremely broad because every movie, series, game, and event could have different spoiler terms and contexts. Starting with a small list of selected sites and user-provided titles would make the project much more manageable.

Identifying the actual spoiler is probably the hardest part. A title or character name doesn’t automatically mean the surrounding sentence contains a spoiler, and you also need rules for when content should become visible again. I’d start with simple user-defined keywords, regular expressions, and page-specific rules before attempting AI-based detection.