What is my Facebook UID and how do I find it?

Your Facebook UID is a unique number assigned to your profile.

To find your UID on Facebook:

1.  Log in to your Facebook account.

2.  At the top of the Facebook page, there is a navigation bar in the upper right corner with options like Home, Profile, and Account. Click Profile.

3. At the top of your browser, you will see a URL that looks like this:

4. The number at the end of the URL, (after php?id=) is your Facebook UID.

If you have a custom Facebook username:

If you have set a custom Facebook username, or "vanity URL," your URL displays the letters and/or numbers that you chose, and not a numeric UID.

If you have the "vanity URL" you can find your Facebook ID by following these steps:

• Go to your profile.
• Move your mouse pointer onto your current Profile Picture.
• If your browser has a status bar enabled at the bottom of the screen, it will show an URL.
• The number behind the dots is your id.  For the example below "123456789" is the ID.
  https://www.facebook.com/media/set/?set=a.111051224565362.24509.123456789&type=1

If you don't have the status bar you can copy the shortcut by right clicking and paste into a text document.

Source: URL