OpenAI Playground Alternative — Test GPT, Claude, Gemini and More Side by Side
The OpenAI Playground is a great tool — for testing OpenAI models. The moment you want to compare GPT-5 against Claude Opus 4.7 or Gemini 2.5 Pro, you have to open three tabs, paste the same prompt three times, and reconcile the latency and cost numbers in your head. freeprompttester.app fixes that. It is a free, browser-based playground that runs the same prompt across up to six models from any combination of OpenAI (via OpenRouter), Anthropic, Google, xAI, Mistral, DeepSeek, Cohere and Groq, and streams every response into its own card with TTFT, latency, token usage and per-call cost shown live.
Like the OpenAI Playground, freeprompttester.app needs no sign-up — you bring your own API keys, which never leave the browser. Unlike the OpenAI Playground, it works for every major provider in a single screen.
freeprompttester.app vs OpenAI Playground
| Feature | freeprompttester.app | OpenAI Playground |
|---|---|---|
| Models supported | 25+ across 8 providers | OpenAI only |
| Side-by-side runs | Up to 6 in parallel | One at a time |
| Streamed output | Yes, with TTFT | Yes |
| Per-call cost shown | Yes, live | No |
| Sign-up required | No (BYO key) | Yes (OpenAI account) |
| Server-side proxy | None — browser ↔ provider directly | OpenAI servers |
| Where keys live | localStorage in your browser | OpenAI account |
| Price | Free (you pay providers directly) | Free + per-token API spend |
| Offline | Yes (PWA shell) | No |
Multi-turn chat that the OpenAI Playground can't do
The OpenAI Playground is essentially single-turn — you tweak parameters, generate, repeat. freeprompttester.app has a dedicated Chat mode that holds a parallel multi-turn conversation with up to three models simultaneously. You set one system prompt, type a message, and every selected model replies in its own column with its own conversation history. The same follow-up question can produce three different threads as the conversation diverges, which is exactly the workflow you want when comparing how Claude, GPT and Gemini stay in character (or break) over 10+ turns. Cumulative cost per column is shown live so you can see when a long chat starts to get expensive.
✦ Synthesize: combine multi-model responses into one answer
After running a single-shot prompt across multiple models, freeprompttester.app's ✦ Synthesize button sends all completed responses to one chosen model and asks it to produce a combined best-of answer with explicit consensus and disagreement sections. Useful for boiling a 4-way model comparison down to a decision-ready output. The OpenAI Playground has no equivalent — it's a single-vendor tool by design.
Why use freeprompttester.app instead?
If you build with multiple providers — or are deciding which one to commit to — single-vendor playgrounds force you to do the comparison manually. freeprompttester.app turns "compare three models on one prompt" into a single click. Outputs stream in parallel, TTFT lets you see how fast each model starts producing text, and the cost field tells you exactly what each call cost so you can spot which model is best per dollar for your specific workload.
What about OpenAI's CORS limitation?
OpenAI's API blocks direct browser calls — if you POST to api.openai.com from a static page, the browser refuses on CORS grounds. That is why so many "playground" tools run a proxy server (and see your keys and prompts). freeprompttester.app skirts this by routing OpenAI requests through OpenRouter, which does support browser calls and offers GPT-5, GPT-5 mini, GPT-4.1 and o4-mini under a single key. The other seven providers freeprompttester.app supports (Anthropic, Google, xAI, Mistral, DeepSeek, Groq, Cohere) all permit direct browser API-key calls, so those go straight from your browser to the provider.
Try freeprompttester.app — Free, No Sign-Up
Bring your own API keys. Up to six models in parallel. Streams in your browser.
Open AI Prompt Tester →Frequently Asked Questions
Is freeprompttester.app really a drop-in OpenAI Playground alternative?
Yes — for any workflow that doesn't depend on OpenAI's UI for fine-tuning files or assistants. freeprompttester.app handles the most common playground use case: write a prompt, pick a model (or several), see the response. It adds parallel multi-provider runs, live cost, and TTFT numbers.
Do I need an OpenAI API key to use freeprompttester.app?
No — you only need keys for the providers you want to test. To use OpenAI models, get an OpenRouter key (which gives you GPT-5, GPT-4.1, o4-mini and others) instead of a direct OpenAI key, since browsers cannot call OpenAI directly.
How is this different from running OpenAI Playground in incognito?
Incognito only changes session persistence on OpenAI. It does not let you compare GPT-5 against Claude Opus 4.7 in one screen. freeprompttester.app does — and runs entirely in your browser.
Are my prompts logged?
No. freeprompttester.app is a static page with no server. Your prompt goes from your browser to each AI provider you select, end of story. There is no Freesuite analytics on input.
Can I export results?
Yes. Click the copy icon on any card to copy a single output. Future versions will support full-run JSON export.
Does it support function calling, image inputs, or fine-tuned models?
Not in v1. freeprompttester.app v1 covers the chat completions surface for each provider. Function calling and multimodal inputs are on the roadmap.