TikTok, by a wide margin. It’s the only major platform left where the algorithm consistently puts a 0-follower account in front of real people. For a solo dev with no audience, that’s worth more than any other lever.
The trap most indie devs fall into is treating it like X or LinkedIn. “Day 12 of building my app” threads mostly die on TikTok. What works is short vertical product demos with the value visible in the first 1-2 seconds. Show the problem, then show the app fixing it. Two posts a day for a few weeks and you’ll start seeing patterns.
The thing most people skip: track which post format is doing the lifting. Talking head vs screen recording vs stitch reaction vs voiceover. Almost always one or two formats end up pulling 80% of your reach once you’ve got 30+ posts up. Most people just chase the algorithm without checking.
(I run palimio.com which automates that kind of analysis. Honestly though, with only a few dozen posts up you can eyeball it in a spreadsheet.)