Someone is asking for a product like yours on Reddit right now. The thread will collect 40 comments in six hours, someone will recommend a competitor, and you'll find it three weeks later when it's already ranking in Google for your category.
Quick answer: Reddit has no built-in keyword alerts — its native notifications only cover replies, username mentions, and followed communities. To get pinged when a keyword appears you need one of five setups: F5Bot (free, exact match), Reddit RSS + Zapier/Slack (free, DIY), Google Alerts (free, days late), a mobile wrapper app, or a semantic tool like Prowlo ($19/mo, also catches threads your exact keywords miss). Setup steps and where each one breaks, below.
Option 1: F5Bot — free email alerts
F5Bot has been the default answer for a decade: enter keywords, get an email when they appear in Reddit posts or comments (plus Hacker News and Lobste.rs). The free plan covers up to 200 keywords.
Setup: create an account, add keywords, done. No dashboard on free — alerts arrive by email only.
Where it breaks:
- Exact match only. "Prowlo" works. "best tool for monitoring subreddits" — the thread you'd actually pay for — never matches.
- Volume caps. On free, a keyword auto-pauses after roughly 50 hits in 24 hours, so a popular term goes quiet mid-day. Paid tiers (~$17/mo Power, ~$70/mo Ultra with API and webhooks) raise the caps.
- Email-only delivery on free, and no history — a deleted alert is gone.
Use it if you're watching 1–3 exact brand terms on a $0 budget. It's genuinely good at that.
Option 2: Reddit RSS feeds + Zapier or Slack
Reddit still exposes RSS everywhere, which makes a DIY pipeline possible without touching the API:
- Search feed:
https://www.reddit.com/search.rss?q=your+keyword&sort=new - Subreddit firehose:
https://www.reddit.com/r/SaaS/new/.rss - Comments:
https://www.reddit.com/r/SaaS/comments/.rss
Setup: pipe a feed into Zapier, Make, or Slack's built-in /feed command; add a keyword filter step; deliver anywhere.
Where it breaks: string-match filtering only, one automation per subreddit or query, silent breakage when Reddit adjusts rate limits, and someone has to own the plumbing. A weekend project that becomes a chore — but you control every piece.
Option 3: Google Alerts with site:reddit.com
The classic hack: create a Google Alert for "your keyword" site:reddit.com. It fires when Google indexes the thread — hours to days after the conversation happened — and it misses most threads entirely. Fine as a free backstop for evergreen mentions; useless for catching a conversation while it's alive.
Option 4: Can Reddit itself notify you about keywords?
Reddit itself will notify you about replies, mentions of your username, and activity in communities you follow — but not keywords. There is no native keyword alert, on web or mobile. Third-party mobile apps ("Alerts for Reddit" on Android and similar) wrap keyword polling in an app; reviews are mixed and they inherit Reddit's API constraints. If you want alerts on your phone, the more reliable path is any tool from this list that delivers to Slack — Slack's mobile notifications do the rest.
Option 5: Semantic alert tools (Prowlo)
The structural problem with options 1–4 is exact matching: the highest-value threads — "anyone know a good GummySearch replacement?" — often don't contain your keyword at all.
Prowlo works differently. You create a Watcher on the subreddits where your buyers are; Prowlo crawls those sources (posts and comments), tags keyword matches, and embeds every record for semantic search — so meaning-adjacent threads surface even without the exact phrase. High-relevance hits go to Slack or a webhook; everything lands in a searchable Dataset, so "what did r/SaaS say about us in March" is a query, not archaeology. Your AI agent can run the same searches over MCP.
Setup: one Watcher — subreddits + keywords + delivery channel. $19/mo flat after a 14-day trial, no card. And it's read-only by design: no auto-replies, nothing that gets your account banned.
If you only need exact-match on one brand name, use F5Bot — seriously. Prowlo earns its money when the threads that matter don't contain your keyword.
The comparison, side by side
How do you cut alert noise? (the part everyone skips)
Ten keywords with no filtering means an hour a day of deleting alerts — the top complaint in every "how do you track Reddit keywords" thread. Four filters, in order of impact:
- Subreddit whitelist. Watch the 5–15 communities where your buyers actually are, not all of Reddit. This kills more noise than any other setting.
- Negative keywords. Track "keyword tracking" and exclude "hiring", "job", "course". Boolean tools (Syften) and prefilter rules (Prowlo) both support this; F5Bot free doesn't.
- Score/age thresholds. A post with zero upvotes after six hours is usually not worth a ping. Prowlo prefilter rules can drop by score, age, language, or repost status before anything reaches you.
- Semantic ranking instead of more keywords. The instinct when you miss threads is adding keyword variants — which multiplies noise. Semantic matching inverts it: fewer keywords, ranked results, and a relevance score you can threshold.
For what to track: brand + misspellings, competitor names, and the five buying-intent phrasings ("alternative to", "anyone recommend", "switching from") that signal someone is actually shopping.
FAQ
Can Reddit notify me when a keyword is mentioned?
No — Reddit's native notifications cover replies, username mentions, and followed communities, not keywords. Every keyword alert requires an external tool: F5Bot (free), an RSS pipeline, or a hosted tool like Prowlo or Syften.
What's the best free Reddit keyword alert tool?
F5Bot: 200 keywords, posts and comments, email delivery, at $0. Its limits are exact-match-only and a ~50-alerts/day cap per keyword on free. Reddit RSS feeds into Slack are the best free option if you want delivery somewhere other than email.
Can I get Reddit keyword alerts on my phone?
Indirectly, and it works better than the app-store options: route alerts to Slack (via Prowlo, Syften, or an RSS pipeline) and let Slack's mobile push handle the phone part.
How fast do alerts need to be?
The useful window for joining a thread is roughly its first 2–6 hours — early comments get the visibility. Faster than hourly rarely changes outcomes; slower than a day means you're commenting into a dead thread.
Do these tools monitor comments or just posts?
It varies, and it matters — many buying conversations happen in comments under someone else's post. F5Bot, Syften, and Prowlo cover both; RSS pipelines cover posts easily and comments only per-subreddit; Google Alerts effectively covers neither in time to act.