To validate a startup idea on Reddit, read before you post: search for people asking for the thing you want to build, count how often they ask, note what they already use and pay for, and only then talk to the ones who asked. Posting "would you use this?" gets polite yeses at best and a removal at worst; the asks that already exist are the evidence.
Search for the words a buyer would type when they have the problem, not the name of your product category. "Is there an app that", "any recommendations for", "alternative to", "what do you use for" and "I would pay for" next to your problem's words find people asking. Your category's name alone finds news, reviews and other founders.
Read the last month, not the last year. An ask from 2021 tells you the problem existed; ten asks this month tell you it still hurts. Old Reddit's search and the subreddit's own search both sort by new, which is the view you want.
Validation on Reddit is a count, not a feeling. Write down every real ask you find with its date and subreddit. If you find several fresh asks a week across a few rooms, the problem is live. If you find one every few months, the problem is real but rare, and rare problems are hard to sell into.
Be ready for low numbers. When we went through small consumer apps by hand in October 2026, it came out at about one fresh ask a week for every eight niche apps. That is normal for a narrow product, and it is why the rooms where people ask matter more than how big the subreddit is.
The replies under an ask are free competitor research. They name the tools people already use, the workarounds (a spreadsheet, a group chat, a paid assistant) and the complaints about both. A problem with an angry "everything I tried is too expensive or too complicated" under it is a better sign than a problem nobody has tried to solve.
Watch for money words: "I'd pay", "we pay for", "cancelled because", "too expensive for what it does". They tell you a budget exists. If every reply recommends a free tool and the asker is happy, the problem is solved for them and your idea needs a different buyer.
The best validation Reddit gives you is a person who described your problem in their own words last week. Reply with a genuinely useful answer first, and if the room's rules allow it, ask one honest follow-up question about what they tried. Ten of those conversations beat a hundred upvotes on a "would you use this" post.
Read each subreddit's rules before you post anything there. Many founder and recommendation subreddits remove posts that look like surveys or self-promotion, and some remove any comment with a link automatically. Decide your pass line before you start, for example five fresh asks this month and two people who reply to your question, so the result can actually say no.
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You can, but it is weak evidence and often against the rules. People are polite about ideas that cost them nothing, and many founder subreddits remove survey and "would you use this" posts. The asks people already wrote, before you showed up, are stronger evidence than any answer to your own question.
The ones where your buyers ask for help with the problem, not the startup subreddits. A recipe app is validated in cooking and meal-planning rooms, a bookkeeping tool in rooms for freelancers and small business owners. Startup subreddits tell you what founders think, which is rarely who will pay.
There is no magic number, but look for repeated, fresh asks: several in the last month across more than one subreddit, with replies that show people already spend money or time on workarounds. One viral post is a story; a steady trickle of asks is a market.
Skip the guesswork. Kasspian finds the people already asking for what you sell, writes the replies, and shows which ones turned into revenue, with the sources behind every call.
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