Why We Built Haamu: The Missing Layer Between You and the Internet
Every piece of text you publish online carries two fingerprints. The first is obvious: names, email addresses, phone numbers, physical addresses — the personal data you might accidentally leave in a document before sharing it. The second is invisible but just as identifying: your writing style.
Sentence length patterns. Vocabulary choices. How often you use commas versus semicolons. Whether you write "however" or "but." These micro-patterns form a stylometric fingerprint that's unique enough to identify authors across anonymous accounts, leaked documents, and whistleblower reports.
We built Haamu to erase both.
The PII problem is solved (mostly)
Tools for removing personal data from text have existed for years. Microsoft's Presidio is excellent open-source software. Cloud services from AWS, Azure, and Google all offer entity detection APIs. If all you need is to strip names and emails from a document, the technology exists.
But PII removal alone gives you a false sense of security. Your anonymized text still sounds like you. For journalists protecting sources, employees reporting misconduct, researchers handling sensitive data, or anyone who needs true anonymity — removing the "who" while keeping the "how" isn't enough.
Style anonymization: the gap nobody filled
Stylometric analysis has been used in academia and forensics for decades. Researchers have de-anonymized authors of underground forum posts, identified the writers behind literary pseudonyms, and attributed leaked documents to specific individuals — all from writing patterns alone.
The defense against stylometric analysis is style transfer: rewriting text so it preserves the meaning but changes the fingerprint. Until recently, this required either a human editor or clunky rule-based paraphrasing tools that produced obviously machine-generated output.
Large language models changed that. A well-prompted LLM can genuinely restyle text — different vocabulary, different sentence structures, different rhythm — while keeping the ideas intact and the output natural. The technology to solve this problem finally exists. But no consumer tool was using it for privacy.
That's the gap Haamu fills.
Why "Haamu"?
"Haamu" is Finnish for "ghost" or "spirit." We're a Finnish company, and the name captures exactly what the tool does: it makes you a ghost. Your personal data disappears, your writing style vanishes, your document metadata is stripped. What's left is the content — clean, anonymous, untraceable to you.
Three layers of protection
Haamu combines three anonymization layers that no other consumer tool offers together:
- PII Ghost detects and removes personal data — names, emails, phone numbers, addresses, national IDs, credit cards, IBANs, IP addresses. Powered by Microsoft Presidio running locally on our server, with custom recognizers for Finnish personal identity codes and addresses. Your text never leaves our infrastructure for this step.
- Style Ghost rewrites your text with a completely different writing style. Same meaning, different fingerprint. Powered by Claude or GPT-4.1 (your choice). The AI is instructed to change vocabulary, sentence structure, tone, and punctuation patterns so the output can't be attributed to the original author.
- Document Ghost (coming soon) strips metadata from files — EXIF data from images, author information from Office documents, revision history, GPS coordinates, software fingerprints. The invisible data that travels with every file you share.
Privacy by architecture
We made deliberate architectural choices to minimize data exposure:
- No accounts required for the free tier. No email collection, no tracking cookies, no analytics scripts. You paste text, get results, done.
- Nothing is stored. All processing happens in memory. We don't log your input text, don't save your results, don't build a history. When the request completes, the data is gone.
- PII detection runs locally. The Presidio engine runs on our server in Helsinki. Your text is never sent to a third party for PII analysis.
- EU infrastructure. Our server is in Helsinki, Finland. PII detection stays entirely within the EU. Style rewriting uses US-based AI providers (Anthropic or OpenAI) — see our privacy policy for transfer details.
- You choose the AI provider. For style rewriting, you pick between Anthropic (Claude) and OpenAI (GPT-4.1). We're transparent about which step sends data where.
Who is Haamu for?
Anyone who shares text and cares about privacy:
- Journalists protecting sources in documents they publish
- Whistleblowers who need writing that can't be traced back
- HR professionals anonymizing employee feedback and reports
- Researchers handling interview transcripts and case studies
- Students sharing notes without exposing personal information
- Anyone posting online who wants one less way to be identified
Try it
Haamu is free to use — 500 words per day, no signup, no credit card. Paste your text, pick a mode, and see what a ghost looks like.