Workspace/Prompt comparison
Open source
✦A LITTLE CONFIDENCE BEFORE YOU SHIP

Small prompts.
Visible differences.

Compare two versions. Check the edge cases.
Find what got better — and what quietly broke.

No API key needed for demo5 test cases · 2 prompt versions · zero setup
MODE
i

A

Baseline

CURRENT VERSION
{{input}}is replaced with each test input
B

Candidate

YOUR CHANGES
{{input}}is replaced with each test input
THE SAME INPUTS. A FAIRER COMPARISON.

Test cases5

LESS GUESSWORK. MORE EVIDENCE.

Comparison results

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A small change deserves a closer look.

Run your first comparison to see outputs, check results and regressions side by side.

Tip: Ctrl / ⌘ + Enter to run

Add a test case

New cases run in live mode. For offline playback, add recorded outputs through Edit JSON.

Connect your model

Run PromptCanary locally. Copy .env.example to .env, fill in your provider settings, then restart the server. 

LLM_BASE_URL=https://api.deepseek.com
LLM_MODEL=your-model-id
LLM_API_KEY=your-api-key

Local compatible servers can use an HTTP localhost endpoint without an API key. Model calls leave your machine for the configured provider.

The hosted demo supports fixture playback only. Live calls require the local Node.js server.

Read setup guide ↗