How Much Do AI API Keys Cost? (The Key Is Free)

By the Zylo team · Updated June 8, 2026 · 5 min read

One of the most common misconceptions among developers exploring AI APIs for the first time is that the API key itself carries a cost. It does not. An API key is a credential — a string that identifies your account to the server so it can attribute token usage to you and enforce rate limits. The key has no intrinsic price; what you pay for is the work the model performs when you use that key. At Zylo, you can create an account, receive an API key, and start making calls to Basic-tier models without entering a credit card or providing any billing information. The separation between holding a key and incurring charges is important to understand because it changes how you approach experimentation: there is no cost to obtaining access, and no cost to holding a key that you use infrequently within the free Basic plan limits.

What the free Basic plan actually covers

The Zylo Basic plan is free in a concrete, practical sense: no card required, no trial period, no expiry. It provides approximately 200,000 tokens and 7,200 requests per day, capped at 10 requests per minute and 200,000 input characters per request, on Basic-tier lightweight models. This is enough to build and test a wide range of applications — chatbots, document summarizers, classification systems, and simple code assistants — before spending anything. The honest boundary is model access: Basic plan keys do not unlock premium models such as Claude Opus 4.8, GPT-5.5, or Gemini 3.1 Pro. Those models require a paid plan with credits. The free API key guide explains the sign-up process in detail and describes exactly which models and capabilities are available without payment, so you can assess the free tier against your actual use case before deciding whether to add credits.

When costs begin: tokens, not keys

Charges begin when you exceed the Basic plan’s daily allowance or when you call a premium model that requires credits. In both cases, what you are paying for is tokens — the input tokens you send and the output tokens the model generates. Zylo bills every model at its published base per-token rate with no markup on usage. A flat 25 percent platform fee applies only when you add credits to your account at top-up, never on individual API calls. This means the per-token cost you see on the pricing page is exactly what your workload costs to run, and the fee is a one-time consideration when funding your balance. For a detailed breakdown of what token costs look like across different models and workloads, the AI API cost guide covers the full pricing spectrum from sub-cent-per-million models to flagship rates, with examples of how to estimate a monthly bill before committing to a paid plan.

Why the key is free but access is not

It can seem odd that the credential costs nothing while using it eventually does, but the split is deliberate and works in your favor. A key is just an identifier; issuing one costs the provider almost nothing, so gating it behind a fee would only discourage the experimentation that leads to real usage. The real cost lives in inference — the compute a model burns to read your prompt and generate a reply — and that is what the per-token rate pays for. Charging for the work rather than the key is also fairer: a developer who holds a key but rarely calls it pays nothing, while a high-volume application pays in proportion to what it actually consumes. This is why “how much does an API key cost” is really a question about usage, and why a free key on a free Basic plan lets you prove out an idea completely before a single charge appears. You scale into cost only as your traffic and your model needs grow.

Comparing the real cost of access across providers

When developers compare AI API providers, the key question is not how much the key costs — because the answer is nearly always zero — but rather how much usage costs, and what you can access before you pay. Different providers have different policies on free tiers, rate limits, and which models are accessible without billing. Zylo’s free Basic plan is a permanent tier, not a time-limited credit grant, which means it is suitable for ongoing low-volume workloads and long-term prototyping. When you do need premium models, the Zylo pricing page lists the Go, Pro, Mega, and Enterprise plans alongside the credits each includes and the rate limits each unlocks. The model catalogue shows which plan tier is required for each model, letting you select the minimum plan that gives you access to the specific models your application needs rather than over-paying for capabilities you will not use.