> For the complete documentation index, see [llms.txt](https://davidjosearaujo.gitbook.io/online-courses/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://davidjosearaujo.gitbook.io/online-courses/api-authentication/tokens/formats.md).

# Formats

## How is it encoded

* By value
* By reference

<figure><img src="https://519089207-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F2A0dg9Wy89z8CRkQMup2%2Fuploads%2FASotqHDIwoDVx2WxtoO0%2F2024-08-09_15-25.png?alt=media&amp;token=51e63cba-772c-4273-8cca-51cf9338f58a" alt=""><figcaption></figcaption></figure>

## Reference

Opaque to the holder

Can not be decrypted or decoded

Requires call to the Authorization server to read and validate

Safer to use on the Internet

### Purpose - who is it for

<figure><img src="https://519089207-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F2A0dg9Wy89z8CRkQMup2%2Fuploads%2FIrZsKgyJ8iWKCdJrOtcr%2F2024-08-09_15-27.png?alt=media&amp;token=a4e0726c-71d5-4beb-bc9e-858071f0f8b8" alt=""><figcaption></figcaption></figure>

<figure><img src="https://519089207-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F2A0dg9Wy89z8CRkQMup2%2Fuploads%2Fw6fLKVHyFNcgrCOpT2BC%2F2024-08-09_15-53.png?alt=media&amp;token=ffb13224-438d-4ea0-9c22-0460a88a183b" alt=""><figcaption></figcaption></figure>

### Type - how can it be used

* Bearer
* Holder of Key (HoK) / Proof of Possession (PoP)