RichTextBox for UWP supports several CSS selectors. The following table lists CSS selectors by pattern and CSS level and notes whether they are supported by RichTextBox for UWP.
| Pattern | CSS Level | Supported |
| * | 2 | YES |
| E | 1 | YES |
| E[foo] | 2 | YES |
| E[foo="bar"] | 2 | YES |
| E[foo~="bar"] | 2 | YES |
| E[foo^="bar"] | 3 | YES |
| E[foo$="bar"] | 3 | YES |
| E[foo*="bar"] | 3 | YES |
| E[foo|="en"] | 2 | YES |
| E:root | 3 | NO |
| E:nth-child(n) | 3 | NO |
| E:nth-last-child(n) | 3 | NO |
| E:nth-of-type(n) | 3 | NO |
| E:nth-last-of-type(n) | 3 | NO |
| E:first-child | 2 | NO |
| E:last-child | 3 | NO |
| E:first-of-type | 3 | NO |
| E:last-of-type | 3 | NO |
| E:only-child | 3 | NO |
| E:only-of-type | 3 | NO |
| E:empty | 3 | NO |
| E:link | 1 | NO |
| E:visited | 1 | NO |
| E:active | 2 | NO |
| E:hover | 2 | NO |
| E:focus | 2 | NO |
| E:target | 3 | NO |
| E:lang(fr) | 2 | NO |
| E:enabled | 3 | NO |
| E:disabled | 3 | NO |
| E:checked | 3 | NO |
| E::first-line | 1 | NO |
| E::first-letter | 1 | NO |
| E::before | 2 | NO |
| E::after | 2 | NO |
| E.warning | 1 | NO |
| E#myid | 1 | YES |
| E:not(s) | 3 | NO |
| E F | 1 | YES |
| E > F | 2 | YES |
| E + F | 2 | YES |
| E ~ F | 3 | YES |