Global search-and-replace operations are not needed as often in Emacs as they are in other editors(In some editors, search-and-replace operations are the only convenient way to make a single change in the text.), but they are available. In addition to the simple M-x replace-string command which is like that found in most editors, there is a M-x query-replace command which asks you, for each occurrence of the pattern, whether to replace it.
The replace commands all replace one string (or regexp) with one replacement string. It is possible to perform several replacements in parallel using the command expand-region-abbrevs . See Expanding Abbrevs.
| Unconditional Replace | Replacing all matches for a string. |
| Regexp Replace | Replacing all matches for a regexp. |
| Replacement and Case | How replacements preserve case of letters. |
| Query Replace | How to use querying. |