> 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="/files/IJBayik5mMKE3Anpgbsp" 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="/files/n9L9J7HxdCstHKToFcI9" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/hIqI7Uux6446zOuGrMjS" alt=""><figcaption></figcaption></figure>

### Type - how can it be used

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