> For the complete documentation index, see [llms.txt](https://help.rzr.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.rzr.com/readme/audience-sharing-setup/hashed-audience-solution-for-privacy-sensitive-retargeting.md).

# Hashed Audience Solution for Privacy-Sensitive Retargeting

RZR supports hashed audience onboarding for advertisers that want to activate retargeting or suppression audiences while reducing direct sharing of raw device IDs. You hash your IDFA, GAID, or IDFV values with SHA256 on your side and share only the hashed file through a secure file upload process. RZR then matches those hashed values against identifiers observed in our ad traffic and builds a campaign-ready audience from the matched users. Final audience size depends on audience overlap.

### What this solves

Some advertisers want to run retargeting or suppression campaigns but are concerned\
about sending raw user-level device identifiers to a partner. RZR’s hashed audience\
workflow lets the advertiser transform the identifiers on their own side before sharing the\
audience file. RZR then uses the hashed values only for audience matching and campaign\
activation.

### How it works

<table><thead><tr><th width="84.2265625">Step</th><th>Advertiser</th><th>RZR</th><th>Result</th></tr></thead><tbody><tr><td>1</td><td>Exports the intended<br>audience list, such as<br>IDFA, GAID, or IDFV.</td><td>No action required.</td><td>Source audience is<br>prepared by the advertiser.</td></tr><tr><td>2</td><td>Applies SHA256 hashing<br>before sharing the file.</td><td>Does not receive the raw<br>identifier list.</td><td>Only hashed identifiers are shared.</td></tr><tr><td>3</td><td>Uploads the hashed file via S3.</td><td>Ingests and validates the<br>hashed file.</td><td>Audience is ready for<br>matching.</td></tr><tr><td>4</td><td>Confirms the campaign<br>use case, such as retargeting or suppression.</td><td>Activates the matched<br>audience for the agreed<br>campaign.</td><td>Matched audience is ready<br>for activation.</td></tr></tbody></table>

{% hint style="info" %}
**Note:** Hashed device files are only supported when shared via S3.
{% endhint %}

### File requirements

* **Hashing method:** SHA256.
* **Supported identifiers:** IDFA, GAID, or IDFV, depending on platform and campaign setup.
* **Format:** Plain-text <mark style="color:$primary;">`.csv`</mark> or <mark style="color:$primary;">`.txt`</mark> file.
* **Structure:** One hashed identifier per line, with no header row.

### Privacy positioning

Hashing reduces direct exposure of raw device identifiers because the advertiser performs\
the transformation before the file is shared. RZR receives the hashed audience file and uses\
it to find overlap with identifiers observed in our ad traffic for the agreed campaign purpose.

### What to expect

The final audience size may be smaller than the uploaded file because only matched\
identifiers can be activated. Match rate depends on file quality, correct identifier type,\
consistent SHA256 hashing, and audience overlap.

***

If you need assistance, reach out to your **RZR Account Manager** or **Account Coordinator**.