Case Studies What building browser extensions taught me
What building browser extensions taught me
TL;DR Across seven browser extensions the recurring lessons are: you are building against interfaces you do not control, so stay resilient and easy to update; Manifest V3 trades power for speed and privacy, so design within its constraints; and the best extensions expose a platform capability simply, with privacy as the default.
Seven extensions in, browser development has taught me a distinct set of lessons from plugin work. Extensions live inside other people's interfaces and inside a platform that keeps changing the rules, and both shape how you build. Here is what carried across all of them.
You build against things you do not control
The defining constraint of an extension is that it operates inside pages and apps you did not build and cannot change. A reader extension parses articles with wildly inconsistent markup. A prompt library inserts into chat UIs that get redesigned. An ad blocker targets patterns that shift.
The lesson is resilience. A selector that works today can break when a site ships a redesign, so you keep the integration points few, simple, and easy to update, and you assume the ground will move. Cleverness that depends on someone else's markup staying still is a liability.
Manifest V3 is a constraint to design within
Across these extensions, Manifest V3 reshaped what is possible: background pages became on-demand service workers, and request blocking moved to a declarative rules API. It trades raw power for speed and privacy.
The temptation is to resent the constraints; the better move is to design within them. The declarative model that makes an ad blocker less freeform is also what makes it fast and private. Working with the platform's grain, rather than against it, produces extensions that are lighter and age better.
Privacy is the right default
A browser extension sits in a position of real trust, close to everything the user does online. The extensions I am proud of treat that seriously: they keep data local, avoid tracking, and do their job without phoning home. A cookie-rejecter, a disposable-inbox tool, a local screen recorder, each is built so the private choice is the default and nothing leaks.
That is not just ethics; it is what makes an extension one people are willing to keep installed. Trust is the whole product.
The through-line
The best extensions expose a browser capability simply and get out of the way. Capture a page, clean up an article, block the trackers, record the screen, each does one clear thing, respects the user, and stays light. It is the same focus that runs through my plugins, applied to a platform where the ground moves under you and the trust bar is higher.
The full set is in the Chrome extensions section of the site.
FAQ
What is the hardest part of building browser extensions?
Building against web pages and chat interfaces you do not control. Their markup changes without warning, so a selector that works today can break tomorrow. The craft is staying resilient and keeping the integration points few and simple so updates are easy.
How did Manifest V3 change extension development?
It replaced runtime request interception and persistent background pages with a declarative rules API and on-demand service workers. That trades some power for better speed and privacy, so you design within the constraints rather than fighting them.
What makes a browser extension worth installing?
Usually that it exposes a useful browser capability simply, without adding tracking or bloat. The extensions people keep are the ones that do one clear thing, respect privacy by default, and stay out of the way.