Free tiers look generous on a pricing page and feel very different in production. The headline number is usually compute or storage, but the limit that ends your free plan is almost always something else: outbound data, build minutes, function invocations, or a quiet rule about commercial use. Knowing which limit binds first is the difference between a project that runs free for years and one that produces a surprise bill in month two.

Egress is the most common killer. Cloudflare Pages is the exception, with unlimited bandwidth on its free tier, but Netlify, Vercel, and GitHub Pages all cap free bandwidth around 100 GB a month, and Netlify's credit system now works out to roughly 15 GB a month once deploys are counted. A single viral post can burn a month of bandwidth in a day. If your project serves images or video, check the egress number before anything else, and put large files on a CDN or object storage with its own free allowance.

Build minutes are the second surprise. Cloudflare Pages gives 500 builds a month, Netlify gives 300 credits that deploys consume, and Vercel's Hobby plan is generous at 6,000 minutes but bans commercial use. A team that deploys ten times a day will hit Netlify's limit in a month even with almost no traffic. The fix is boring but effective: deploy from your own machine for experiments, and reserve the hosted builds for production.

Function invocations and execution time are the third limit. Serverless free tiers typically allow around a million invocations a month, which sounds enormous until a polling loop or a chatty client calls an endpoint every few seconds. Database limits are the fourth: Supabase's free tier pauses after a week of inactivity and caps storage at 500 MB, while Neon limits egress to 5 GB. The fifth is the idle rule: Render's free web services spin down after 15 minutes without traffic, which means the first visitor waits 30 to 60 seconds for the service to wake up.

The sixth limit is the one vendors rarely advertise: commercial use. Vercel's Hobby plan is for personal, non-commercial projects only, and running ads on the site counts as commercial. GitHub Pages has the same restriction for business sites. The seventh is the account-level rule: Oracle's Always Free tier reclaims idle instances, and several providers require a card on file before the free tier activates at all, which means an accidental click can start billing.

The practical defense is a monthly limits review. Once a month, open each provider's usage dashboard and check the four numbers that matter: bandwidth used, build minutes used, function invocations, and database size. Set billing alerts at 50 percent and 80 percent of every free allowance, and keep a second provider in mind for the service most likely to outgrow its tier. Free tiers are a genuine gift for small projects, but only for projects whose owners know exactly where the free part ends.

One more limit hides in the terms of service rather than the pricing page: the fair-use and abuse clause. Providers reserve the right to throttle or suspend accounts whose usage looks like abuse, and the definition is theirs, not yours. A free tier used to serve a popular open-source project's downloads, or to proxy traffic for others, can be suspended without a billing event at all. Read the acceptable-use section once, keep your usage clearly personal or clearly within the stated project scope, and keep a backup host in mind for anything that becomes genuinely popular, because popularity is the fastest way to outgrow a free tier.