How to use this
Pick what you're building at the top. Each card is one API that can do the job, with a one-line take and four tags: how it's priced, its free tier, how fast you can get a working key, and what it's best suited for. The hidden cost line is the one most estimates miss — the per-number fees, egress, output tokens, payout charges or domain warm-up that quietly inflate the bill after launch.
Use the sort control to reorder: Cheapest first for side projects, Best free tier to prototype without spending, Easiest setup when you want a key in five minutes, or Best overall for a balanced pick. Toggle No credit card and Production-ready to narrow the list to what actually fits your stage.
Common mistakes when picking an API
- Comparing only the headline number. The big figure on a pricing page rarely includes the add-ons. SMS has carrier fees and number rental; email needs a dedicated IP or domain warm-up at scale; maps bill per SKU; payments take payout and FX fees on top of the percentage.
- Optimising for "cheapest" at the wrong stage. For a prototype, a generous free tier beats a fraction-of-a-cent price difference. For production, reliability, rate limits and support matter more than the last few cents.
- Ignoring output tokens on AI APIs. Output is usually 3–5× the price of input. A model that looks cheap on input can be the expensive one once it starts generating long answers.
- Forgetting deliverability and verification. A cheap email or SMS API is worthless if messages land in spam or numbers need manual verification you can't scale.
From shortlist to a real number
Once you've picked two or three candidates, don't stop at the per-unit price — model the monthly bill at the volume you actually expect. Drop your usage into the AI app cost estimator or the API stack cost calculator to see the cost at 1k, 10k and 100k users, and check the free API tiers database to see how far you can get before paying anything.
Many of the APIs below have a full guide here with current pricing and step-by-step key setup — follow the links on each card, or browse all API guides.