[ 10 / comparison — presidio ]
Synthaveil and Presidio.
What it is
An open-source Python toolkit, started at Microsoft and run since June 2026 by the independent Data Privacy Stack project. It finds sensitive values in text and replaces them with placeholder tags, hashes, masks or values from a fake-data library. You run it yourself, wherever you like, and you wire up everything around it.
Where it wins
Presidio supports custom operators, including realistic replacements through Faker examples, and reversible operators. It is worth evaluating if you want a toolkit you can extend and operate yourself.
Where we differ
Compare the configured replacement policy and consistency scope. A tag-versus-name comparison alone does not describe what Presidio can do.
| Capability | Synthaveilthis site | PresidioOpen-source detection and redaction |
|---|---|---|
| Runs inside your own environment | yes | yes |
| No generative AI or large language model reads your real data | yes | partly |
| Output keeps its shape — a name looks like a name, a date like a date | yes | partly |
| Consistent results without a stored table of real-to-fake values | yes | partly |
| Nothing held at the vendor that could reverse it | yes | yes |
| Replacement matched on statistical character, not only on format | yes | not verified |
| Location stand-ins that keep the area useful without pointing back to it | yes | not verified |
| Stand-ins go stale on a schedule | yes | not verified |
| Reversible on your side when you need the real value back | yes | partly |
| An audit record for every policy decision | yes | not verified |
| Works on live traffic, not only batch jobs | yes | yes |
| Word, Excel and browser add-ins | yes | not verified |
| Stand-ins built from official public statistics | yes | not applicable |
| Detection across many languages and file types | partly | partly |
| Free to use | no | yes |
Source: Presidio documentation
Can the stand-in values be turned back into the real values?
Yes, on your side. When an AI tool replies using stand-ins, Synthaveil puts the real values back, so the answer reads with your real names and is ready to use. Alias, Cover and Legend all restore values; each product page sets out how.
Is pseudonymised data still personal data under GDPR?
For you, yes: you hold the key, so it remains personal data in your hands. The EU Court of Justice (EDPS v SRB, 2025) and the ICO (2025) both look at whose hands the data is in: a recipient with no key, no mapping and no other route to the person may not hold personal data at all. That is what Synthaveil sends an AI provider: stand-ins with no route back. Your duty to tell people about the sharing still applies when you collect their data.
Does Synthaveil make my data anonymous?
No. Synthaveil makes no claim that its output is anonymous. In your hands it remains personal data, because you hold the key. What changes is what the recipient gets: stand-ins with no key or mapping to link them back. Review the remaining context before you share.
Do you have to store a mapping table to keep pseudonyms consistent?
No. Synthaveil keeps stand-ins consistent without storing any real-to-stand-in pairs. Products that restore values keep that information on your side, in your browser, workbook or n8n environment, and it needs protecting.