Should you build your own SubSignal?
Watches Reddit for people describing the problem you solve, and surfaces them as leads
Do not mistake the loop for the product. Polling subreddits and asking a model "is this a buying signal?" is an evening, and it is also the part that does not matter. What makes this useful is the accumulated archive behind it: years of threads at a scale you cannot backfill, which is what lets it tell a recurring complaint from a one-off and rank a lead against everything already seen. Your build starts empty on day one and stays empty, because Reddit will not sell you the past. That is a data problem, not a code problem.
ENOriginal research content in English. Original prompt preserved in English.
Build a Reddit buying-signal monitor inspired by SubSignal.
Use exactly this stack: Node.js 22 + TypeScript + SQLite.
Primary job: on a schedule, fetch new posts and comments from a configured list of subreddits, ask one language model whether each one describes a problem the user's product solves, and deliver the matches to Slack or email with a link and a one-line reason.
Start from an empty folder and create the complete working project.
Use the official Reddit API with credentials from .env and respect its rate limits and terms of use; never scrape around them.
Store every item you have seen in SQLite so the same thread is never delivered twice, including across restarts.
Let the user describe their product in plain language in a config file, and build the classification prompt from that rather than from a hardcoded keyword list.
Score each match and let the user set a threshold, so the digest can be tightened without code changes.
Send a digest rather than one alert per hit, and make the schedule configurable.
Alert the user when a run fails or returns nothing for several consecutive runs - a silent crawler is the main failure mode of this kind of tool.
Put every secret in .env and provide .env.example.
Deliberately exclude these paid-product advantages: a curated subreddit and keyword set, accumulated cross-customer history, managed uptime.
Do not fake integrations, deliverability or data you do not have.
Write unit tests for deduplication and scoring, and one end-to-end smoke test against recorded fixtures rather than the live API.
Create a README with setup, Reddit API terms, cost estimate, architecture and limitations.
Run the tests and build before finishing, then fix what fails.The prompt opens pre-filled in your agent. Review it before running.
What would building your own look like?
Poll a list of subreddits on a schedule, filter new posts by keyword, ask one model whether each is a buying signal for your product, and send the hits to Slack or email.
What you will need
- Reddit API credentials, within Reddit's terms of use
- OpenAI or Anthropic API key in .env
- Node.js 22 and a scheduler such as cron
- SQLite to remember what you have already seen
Because relevance comes from history. Judging a single post in isolation is what a prompt does; knowing that this complaint has surfaced eleven times this quarter and twice from the same team requires an archive. You can start collecting today and be useful in a year, or pay for the year someone else already spent.
xa historical archive you cannot backfill from the live API
xranking a lead against everything seen before, instead of judging it alone
xa curated subreddit and keyword set you did not have to discover
xdeduplication and history across runs
xsomeone tracking Reddit API terms and rate-limit changes for you
Prefer something ready-made?
F5BotReddit keyword alerts by email; no dashboard, no scoring, no theatre.Free↗License, setup, and limitations for each alternative.
How much does SubSignal cost?
- Monthly billing
- $29.99/mo$29.99/mo
- Per year
- $360/yr$360/yr
- Annual billing
- $199/yr45% cheaper than paying monthly
- On a Brazilian card, with 3.5% IOF
- R$157/moR$1,040/yr
Saved to My list. You will see a notice on this site when the price changes.
You complete the purchase on SubSignal’s site. Vibe Radar does not handle payments.
| Plan | Monthly | Annual (per month) | What is included |
|---|---|---|---|
| free | $0/workspace | $0/workspace | Free Reddit tools/monitoring entry point; exact numeric lead/search caps not published on crawled official pages. |
| pro | $29.99/workspace≈ $29.99 | $16.58/workspace≈ $16.58 | Reddit monitoring and lead detection; exact alert/keyword/lead caps not published on crawled official pages. |
Free tierfree tier exists, but numeric monitoring/lead caps were not published on crawled official pages.
Billing termsmonthly + yearly implied; Pro $29.99/mo and from about $16.58/mo yearly on official alternative page
Additional costsMain pricing table not found; exact alert/keyword/lead caps and overage rules remain unverified.
verified 2026-08-10 · source ↗
Is it cheaper to build or buy SubSignal?
Adjust the numbers: hours to build, your hourly rate, running costs and the subscription price.
Over 24 months, subscribing is cheaper.
Starting hours estimated from the analysis (not a true replacement; the loop in one sitting, the corpus never). Does not price what you give up (support, integrations, security).
Can I rebuild SubSignal?
Not really. SubSignal’s value is not the code: The moat is a years-deep Reddit archive you cannot backfill from the live API. See the honest breakdown above.
How much does SubSignal cost?
SubSignal costs about $29.99/mo (Growth, checked 10/20/2026), which is $199 per year.
What do I lose by replacing SubSignal?
Honestly: a historical archive you cannot backfill from the live API; ranking a lead against everything seen before, instead of judging it alone; a curated subreddit and keyword set you did not have to discover; deduplication and history across runs; someone tracking Reddit API terms and rate-limit changes for you. If any of those are load-bearing for you, keep paying.
Is there an open-source alternative to SubSignal?
Yes: F5Bot (Reddit keyword alerts by email; no dashboard, no scoring, no theatre.) The prompt is for when you want it exactly your way.