# Delivery & Security (SRI)

Pushly supports loading a pinned, immutable version of the Web SDK using Subresource Integrity (SRI).

This option is intended for customers with strict security requirements, such as enforced CSP policies. Most customers should continue using the Latest SDK.

***

#### When should I use SRI?

Use SRI only if you require:

* Cryptographic verification of third-party scripts
* Enforcement of `require-sri-for script` in Content Security Policy
* Explicit control over when SDK updates occur

If you do not have these requirements, use the [Latest SDK](/integration/web-push/quick-start.md) instead.

***

#### Pinned SDK snippet example (SRI)

```html
<script
  src="https://cdn.p-n.io/sdk/web/pushly@3.1.0.min.js"
  integrity="sha384-REPLACE_WITH_HASH"
  crossorigin="anonymous"
  async
  data-domain-key="DOMAIN_KEY">
</script>
```

This loads a specific SDK version that will never change.

***

#### Get the integrity hash

The integrity hash for each SDK release is published in a release manifest.

For version 3.1.0:

```
https://cdn.p-n.io/sdk/web/releases/3.1.0/manifest.json
```

Look for the `files[].integrity` field and copy its value into the `integrity` attribute.

***

#### Upgrading a pinned SDK

Pinned SDKs do not auto-update.

To upgrade:

1. Update the SDK version in the script `src`
2. Update the corresponding `integrity` hash
3. Deploy the updated snippet

```diff
- src="https://cdn.p-n.io/sdk/web/pushly@3.1.0.min.js"
- integrity="sha384-OLD_HASH"
+ src="https://cdn.p-n.io/sdk/web/pushly@3.2.0.min.js"
+ integrity="sha384-NEW_HASH"
```

If you do not update the snippet, your site will continue running the older SDK indefinitely.


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