Lettertrace

What is Lettertrace?

Lettertrace is a free, open-source monitoring tool that measures how often AI assistants like Claude, ChatGPT, and Gemini mention your company. It turns raw AI answers into actionable visibility metrics—brand visibility, share of voice, sentiment, and prominence—across topics, models, and time. Unlike typical SaaS trackers, Lettertrace is developer-first and bring-your-own-key, meaning you supply your own Anthropic, OpenAI, or Google API credentials and run everything on your own infrastructure.

Who it's for

• AEO/GEO specialists — teams tracking AI engine optimization who need hard numbers on visibility and share of voice across multiple models.
• Developers and self-hosters — engineers who want full control, MIT-licensed code, and the ability to fork, inspect, and extend the tool without vendor lock-in.
• Brand and product marketers — professionals monitoring how AI answers recommend their product versus competitors like Notion or Linear, and whether sentiment trends positive or negative.

Key features

Bring your own key

Use your own Anthropic, OpenAI, and Google API keys. They're encrypted at rest and never leave your infrastructure, so there's no usage markup and no middleman.

Multi-model monitoring

Track Claude, ChatGPT, Gemini, and Google AI Overviews side by side. You can add more answer engines as they become relevant, all from a single dashboard.

Variation generation

Turn one topic—like "best CRM for startups"—into dozens of natural prompts automatically. Lettertrace writes the real questions people put to AI assistants, so you monitor how they're actually answered.

Sentiment and share of voice

Know not just if you appear, but whether the answer speaks well of you and recommends you. See exactly how often you win the answer versus each competitor you track, with sentiment scores and share-of-voice percentages per topic.

What stands out

"Free end-to-end, developer-first, and open source—no usage markup, no middleman."

That's the core edge. Most AI visibility tools charge per query or per seat, but Lettertrace is completely free and self-hosted. Your data lives in your own Supabase instance, and the MIT license means you can run it, inspect it, and make it yours. The CLI workflow—lettertrace run --project acme—feels native to developers, while the scheduled monitoring option lets you build trend lines on autopilot.

Worth checking out if…

You're already paying for AI API access and want to understand your brand's presence in AI answers without adding another subscription. It's especially valuable if you're technical enough to self-host with Supabase and npm, or if you need competitor benchmarking and sentiment tracking across multiple models. If you're just starting with AEO/GEO, the free entry point and automatic prompt variation generation make it a low-risk way to begin measuring your AI visibility.