All four can be used for free, but two come with conditions worth knowing up front:
Claude Code costs money on its own subscription. But it can be pointed at another provider: two environment variables connect it to a model with a free tier. Which providers have free tiers, and their limits, are listed one by one in the previous resource, 103.
There's a snag: Claude Code expects an endpoint that speaks Anthropic's format, while most free providers speak OpenAI's. So you need a translating layer in between (a proxy like LiteLLM). This is where everyone gets stuck; even with a free provider, pasting the URL straight in won't work.
If you install LiteLLM, watch the version
On 24 March 2026, LiteLLM's PyPI versions 1.82.7 and 1.82.8 were poisoned with credential-stealing code targeting SSH keys, cloud credentials and crypto wallets. The package was pulled and restored, and the current release is clean. Installing without pinning a version gets you the current one; but if you see a command pinning a specific version somewhere, make sure it isn't one of those two.
On the 21st.dev side, searching, publishing and managing are free; installing components is capped at two a day, and generating AI variants needs credits. Exploring is free; mass production isn't.