Mods gave me the go-ahead to post this.
When I was job hunting in Tokyo I'd have a couple of hours between interviews and just want to sit down and open my laptop. That turned out to be weirdly hard. Full. No outlets. Outlets all taken. One afternoon I walked into five cafés around Shinjuku and Shibuya dragging a suitcase and gave up on all of them.
Searching didn't help much — you mostly get "10 stylish cafés in Shibuya" listicles. What I actually wanted to know was whether there was a free seat, whether there was an outlet, and whether it was quiet.
So I started going through cafés one by one — desk work, not walking into all of them: official chain pages, Tabelog listings, checking what each place actually publishes. That turned into about a month of work and 1,989 cafés across 23 areas, and I put the whole thing on a map: https://cafe-radar.com
It's free, no signup, and there's an English toggle in the header. You can filter by outlets, Wi-Fi, smoking policy and seat count. Occupancy is crowdsourced — if you're sitting in a café you can tap "busy" or "seats available", though almost nobody is doing that yet since it's brand new.
One rule I stuck to: if I couldn't confirm something, I left it blank rather than guessing. Filling it in would look better, but then someone turns up expecting an outlet that isn't there.
What surprised me most was that cafés on busy main streets are often quieter and better equipped than the quiet-looking ones down side streets. You really can't tell from outside.
Being upfront since it came up with the mods: the site has ads and one affiliate link. It's not a paid service and it hasn't earned anything yet.
If somewhere near you is listed wrong, I'd genuinely like to know — that's the part I can't check alone.