How to Get Your AI API Key
CatchDiff supports Bring Your Own Key (BYOK) — you can use your own API key from Anthropic or OpenAI to get AI-powered summaries of your PDF comparisons. Your key stays in your browser and is never stored on our servers.
Option 1: Anthropic (Claude AI)
CatchDiff uses Claude Haiku — Anthropic's fastest and most affordable model (~$0.001 per summary).
- 1
Create an Anthropic account
Go to console.anthropic.com and sign up with your email or Google account. It's free to create an account.
- 2
Add billing (pay-as-you-go)
Go to Settings → Billing and add a payment method. Anthropic charges per API call — CatchDiff uses the cheapest model (Haiku), so each summary costs roughly $0.001–$0.003. You can set a monthly spending limit to stay in control.
- 3
Create an API key
Go to Settings → API Keys → Create Key. Name it something like "CatchDiff". Copy the key — it starts with
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Paste it in CatchDiff
In the comparison viewer, click the ⚙ gear icon next to the AI Summary button. Select Claude (Anthropic), paste your key, and click Save key. Your key is stored in your browser only.
Option 2: OpenAI (GPT)
CatchDiff uses GPT-4o mini — OpenAI's most affordable model (~$0.001 per summary).
- 1
Create an OpenAI account
Go to platform.openai.com and sign up. This is the API platform — separate from ChatGPT.
- 2
Add billing
Go to Settings → Billing and add a payment method. OpenAI charges per API call — GPT-4o mini costs roughly $0.001–$0.002 per summary. You can set a usage limit.
- 3
Create an API key
Go to platform.openai.com/api-keys → Create new secret key. Name it "CatchDiff". Copy the key — it starts with
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Paste it in CatchDiff
Click the ⚙ gear icon in the comparison viewer, select GPT-4o mini (OpenAI), paste your key, and click Save key.
Frequently Asked Questions
- How much does it cost?
- Each AI summary costs about $0.001–$0.003 (less than a penny). 100 summaries would cost roughly $0.10–$0.30. Both providers let you set monthly spending limits.
- Is my key safe?
- Yes. Your key is saved in your browser's local storage only. It's sent to our server per-request to call the AI, but it is never stored, logged, or shared. You can clear it anytime from the ⚙ settings.
- Can I use the free trial first?
- Yes — every user gets 30 free AI summaries per month without needing an API key. You only need your own key after that, or if you want unlimited use.
- Which provider should I choose?
- Both work great. Claude (Anthropic) tends to give slightly more detailed summaries. GPT-4o mini (OpenAI) is equally fast and affordable. Pick whichever you already have an account with.
- What does CatchDiff send to the AI?
- Only the text differences (not full documents) — up to 10 changed pages, trimmed to 250 characters each. This keeps costs low and limits data exposure. See our AI disclaimer for details.
CatchDiff is an independent service. We are not affiliated with, endorsed by, or sponsored by Anthropic (Claude), OpenAI (GPT), or Google (Gemini). All trademarks belong to their respective owners.