Not four names for the same generator.
Glitch text adds combining marks. Mirror and upside-down text use different Unicode lookalike maps. Reverse text changes sequence only. Keeping those behaviours distinct makes each page useful on its own.
These tools do different jobs. Pick a transformation, type your text on its page and copy the result without uploading anything or creating an account.

Similar effects stay together, while transformations that behave differently get their own focused tool.
Stack combining marks at light, medium or heavy intensity.
Open glitch tool →Reverse the line and swap supported letters for reflected-looking Unicode.
Open mirror tool →Use rotated-looking Unicode equivalents with reversed order.
Open upside-down tool →Reverse characters, each word, or the order of whole words.
Open reverse tool →Glitch text adds combining marks. Mirror and upside-down text use different Unicode lookalike maps. Reverse text changes sequence only. Keeping those behaviours distinct makes each page useful on its own.
Decorative Unicode and combining marks may be announced unexpectedly by screen readers or rendered inconsistently by devices. Use effects for short decoration and keep essential information in ordinary text.
These pages are closely related to what you are using here.