---
title: "Identify signed-in users | Logdash Docs"
description: "Pass the signed-in user to identify to measure retention and returning visitors. The ID is hashed in the browser and never leaves it."
url: https://logdash.io/docs/web-analytics/identify
---

# Identify signed-in users

Pass the signed-in user to identify to measure retention and returning visitors. The ID is hashed in the browser and never leaves it.

Anonymous visitors get a new ID every day, so retention and returning visitors are measured for identified users only. Once your app knows who is signed in, pass their user ID to `identify`.

##  Call identify

The identity lives in memory only, so call it on every page load, and call it with `null` when the user signs out.

 On every page load, once the user is known 

```javascript
window.logdash?.identify(user.id);
```

 On sign-out 

```javascript
window.logdash?.identify(null);
```

The script is deferred, so your app can know the user before it has loaded. If `window.logdash` is still undefined at that point, call `identify` from the `load` event of the script element.

##  What identify accepts

- `id` is a string or a number. `null`, `undefined` or an empty string clears the identity, and events tracked after that are sent without a user ID.
- A value that contains `@` or is longer than 256 characters is ignored with a console warning and leaves the identity as it was, so an email address is never sent by mistake.
- Events of the page load that are still waiting to be sent when the hash is ready get the user ID too, so the first pageview is attributed when `identify` follows within about a second.

Pass a stable internal ID, never an email address or a name.

##  How the ID is hashed

The tracker hashes the ID in the browser as `sha256(siteId + ':' + id)`, so the raw ID never leaves it. Hashing needs `crypto.subtle`, which browsers offer only in secure contexts such as HTTPS pages. Without it, `identify` does nothing.

Your apps can pass the same user as `userId` with [their own events](https://logdash.io/docs/web-analytics/app-events), and the server computes the same hash, so one user is one person across your website and apps. [Web analytics and privacy](https://logdash.io/docs/web-analytics-privacy#signed-in-users) has the details.