Building a browser extension is technically approachable — a manifest file, some scripts, a small interface — and the parts that actually determine whether it succeeds are the review process and the permissions it asks for, both of which are largely outside the developer's control once the extension is submitted. Chrome's Manifest V3 in particular restricted what extensions can do with background processes, and any extension design predating that shift needs re-architecting rather than a minor patch.
Permissions are the first thing a cautious user checks before installing, and an extension requesting broad access — reading and changing all data on every website visited — for a feature that only needs access to one specific site will be declined by exactly the security-conscious users a business tool most wants to attract. Requesting the narrowest permission set the feature actually needs, and explaining clearly in the listing why each permission is required, converts more installs than any amount of marketing copy.
Store review timelines vary and are worth planning around rather than assuming. Chrome Web Store review can take from a few hours to several days, and a rejection for an unclear reason is common enough that the first submission should be treated as a test run rather than assumed to sail through. Firefox's review process differs again, and an extension distributed across multiple browsers needs separate submission and review cycles for each.
Updates ship faster than a native app's do but aren't instant, and an extension that depends on a website's structure — reading specific elements off a page — is fragile to that website changing its layout with no warning. Building in graceful degradation, where the extension fails quietly rather than breaking the page entirely when its assumptions about a site's structure no longer hold, is what keeps user trust intact between the moment something breaks and the moment a fix ships through review.
