AI Prompt Diff

AI Prompt Diff tool

🔒 Runs in your browser · No uploads · Your data never leaves your device

How to use

1. 1

   Enter both prompts

   Paste your original prompt in v1 and the updated version in v2. The diff updates automatically.

2. 2

   Select a model

   Choose the LLM you're using to see the cost impact of the change in $/call.

3. 3

   Review the diff

   Green lines (+) were added in v2. Red lines (−) were removed. Unchanged lines appear in gray.

4. 4

   Copy as markdown

   Click 'Copy as markdown' to get the diff with +/- prefixes for sharing in GitHub issues, Notion, or Slack.

Common use cases

• Reviewing prompt changes before deployment — Diff the old and new system prompt to confirm what changed and see the token cost impact before shipping.
• Auditing prompt revisions — Copy the markdown diff to share with teammates in GitHub or Notion for review of prompt changes.

Examples

• Adding an expert persona

  Compare a basic 'helpful assistant' prompt to a detailed expert persona

  Output

  +4 lines added, +18 tokens, +$0.00009 per call (GPT-4o)

Frequently asked questions

How are tokens calculated?

Token counts use an approximation of ~1 token per 4 English characters. Actual API token counts may vary by ±5% depending on the model's tokenizer.

Are my prompts sent anywhere?

No. All processing happens in your browser. Your prompt text never leaves your device.

What does the cost delta mean?

The cost delta shows how much more or less you'll pay per API call with the new prompt, based on the input pricing of the selected model.

Key concepts

Prompt diff

A line-by-line comparison of two prompt versions, showing additions (green) and removals (red).

Token delta

The change in token count between two prompt versions, used to estimate the cost impact of a prompt edit.

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