Building software is cheap now. Knowing what to build is the hard part. Every day I scan public Chrome Web Store data for extension openings, then have an AI research each one and judge whether it's worth building. The calls can be wrong; if you spot one, tell me in the comments. (This is issue #2 of my weekly picks newsletter on Substack.)
Five openings from this week's daily lists (Oct 5–10), two directions we rejected, and where our own three extensions stand.
Each pick has the same four parts: what to build, the signal, why now, and the biggest risk. A "signal" is our reason a gap might exist. This issue uses four:
- Abandoned Users: a popular extension was removed or broke, and its users haven't found a replacement.
- Leader Went Bad: the leader was sold, added ads, raised prices or asked for more permissions, and its rating is sliding (neither example this week is the classic case; noted below).
- Leader Complaints: the leader's bad reviews cluster on a problem a new product could fix.
- Unfair Pricing: people pay monthly for something that could be a one-time purchase, free, or bring-your-own-key, and they complain (pick #4 has no complaint evidence yet; noted below).
1. A replacement for Disable HTML5 Autoplay
What to build: a blocker rebuilt on Chrome's current extension format that reliably stops videos from autoplaying, with per-site settings.
Signal: Abandoned Users
Why now: it had about 60,000 users when it was removed around Aug 31, 2026. A month later, judging by how fast the alternatives grew, almost none of those users have been picked up, and the alternatives are rated 1.8 to 3.3. The research judged the removal came from Chrome retiring the old extension format, not from a policy breach, so a rebuild should avoid the same fate.
Biggest risk: users in this category are down 84.0% year over year. There's no evidence yet that the people who lost it will come looking for a replacement.
2. A cleaner Tasks for Canvas
What to build: a simple assignment sidebar for students on Canvas, Blackboard and D2L Brightspace, with a progress ring and streaks, and no drift into AI or GPA features.
Signal: Leader Went Bad
Why now: Tasks for Canvas fell from 4.09 to 2.86 stars. Bad reviews name specific regressions: the progress ring is gone, streaks were reset, and Blackboard support doesn't actually work. The research confirmed these, and so far only open-source projects are catching the people looking to switch.
Biggest risk: demand doesn't look like it's growing (we're re-checking that number). And the damage came from the team's own feature push, not a sale or a price hike, so if they roll it back, the gap may close.
3. Dual subtitles for language learning
What to build: show subtitles in two languages on Netflix and YouTube, with hover-to-translate and a word list.
Signal: Leader Complaints
Why now: the two leading extensions stopped working on Netflix subtitles around the same time. The leaders have 147 bad reviews. The research judged the problem comes from server-side dependencies and per-site adapters, something a front-end-only build can fix, and switching costs for users are low.
Biggest risk: demand is barely growing, and everything hangs on Netflix's player. One redesign and it can break again. This is a window, not a moat: good for a fast test, not a revenue bet.
4. Profit calculator for Mercado Libre and Shopee sellers
What to build: on Mercado Libre and Shopee product pages, show real take-home profit in one click, plus estimates of rivals' prices and sales. One-time purchase, no account, data stays in the browser.
Signal: Unfair Pricing
Why now: every incumbent the research found is a subscription with annual lock-in: JoomPulse at R$297–714 a month, Hunter at R$97–397 a month on a 12-month plan, and no buy-once option. Demand is up 73.3% year over year, and extensions launched in the last 18 months hold 19.0% of the users.
Biggest risk: the pitch is a lower total price, and we haven't found users complaining about price yet. Whether a one-time price sells, and whether collecting payments in Brazil works, both need a cheap test first. Also see the first rejection below: the day before, we turned down something very similar.
5. A steadier alternative to Mo'Kick
What to build: a chat add-on for heavy Kick viewers and moderators, covering what Mo'Kick does but stable first, and built to run alongside 7TV emotes.
Signal: Leader Went Bad
Why now: Mo'Kick slid from 4.68 to 4.46 stars and averaged 3.88 over the last three months. The research judged it wasn't a change of owner but feature bloat and lost stability. Since March 2026 its bad reviews have centred on chat crashes and conflicts with 7TV. Demand is up 316.8% year over year.
Biggest risk: an alternative, NipahTV, has already picked up part of the audience, so this is a validation project, not a revenue one.
Two directions we rejected
- Latin America seller analytics (Unfair Pricing), rejected Oct 8: a mature, crowded market (Nubimetrics, Avantpro, Modelar, EVA Pro, JoomPulse). These tools earn their keep by collecting competitor data over time and keeping estimate models updated, which clashes with a pay-once, browser-only product. We also found no evidence of users complaining about price.
The next day, pick #4, also for Latin American marketplace sellers and also Unfair Pricing, came back as worth building. I'm publishing both calls. We can't tell from the verdicts alone which one is right, so #4 is labelled a cheap test, not a serious investment. AI research can contradict itself from one day to the next, and that's something we have to keep watching.
- Kahoot answer helpers (Unfair Pricing): the core feature is cheating on quizzes. That's a hard line for us, and Kahoot's acceptable use policy bans this kind of automation too. However big the demand, we wouldn't recommend building it.
Our own three extensions
We launched three extensions on Sept 28 and 29 and published four-week success criteria that same week. The day-7 check (organic installs only, promo traffic excluded):
- 03 Bookmark Rewind (Leader Complaints): 1 of 4 criteria met (the search-ranking one); organic installs ≥300, rating ≥4.3 and uninstall rate <40% are not met or have no data yet.
- 02 Reopen Closed Tabs (Abandoned Users): 0 of 4 met (installs, search ranking, rating and uninstall rate all not met or no data yet).
- 01 Page to Markdown for AI: still missing the developer-console export, so no check yet.
Day 7 is early. The full four-week check lands around Oct 26, misses included.
Over to you
Which of these five would you try first, and why?
Any of these can be claimed: one person per opportunity, and we build it for free through to store launch. We take 1 a week, in order of confirmation. All claimable openings: https://numberandreason.com/opportunities/?src=en-dv-weekly
Or leave a comment with a direction you're weighing, and we'll send back a free verdict (1 a day). Here's what a report looks like: https://numberandreason.com/sample-report/?src=en-dv
Data: Chrome-Stats (processed by us) and public Chrome Web Store pages.
— Reid
Top comments (0)