# Regular expressions in filters and replaces

Language: en
Canonical: <https://flowin.click/en/articles/regular-expressions>
Published: 2024-08-21T08:47:17+01:00
Modified: 2025-06-18T12:35:06+01:00

## Regular Expression features

Regular expressions are special text templates that are used to find and match certain strings of characters in the text.

Regular expression support in [filters](<https://flowin.click/posts/filtering-forwarded-messages/>) and [replaces](<https://flowin.click/posts/replacements-in-forwarded-messages/>) in our service allows you to:

- Add any text to the beginning or end of messages.
- Filter messages with any links.
- Delete links, phone numbers, email, and other contact information from copied messages.
- Filter long messages or vice versa only short ones.

To activate the syntax of regular expressions, you must activate the corresponding option in the filter or replacement settings dialog.

## The syntax of the controls

To start using regular expressions, you need to know the syntax, i.e. understand what certain characters mean.

**Main characters**

- ` ^ ` - the beginning of the text
- ` $ ` - the end of the text
- ` . ` - any character
- ` \d ` - any digit
- ` \w ` - any verbal character (Cyrillic, Latin, numbers, "\_", etc.)
- ` \n ` - line break character (new line)
- ` \t ` - tab character
- ` \s ` - all whitespace characters

**Quantitative characters**

Quantitative symbols indicate the number of characters or groups facing them.

- ` * ` - 0 or more times
- ` + ` - 1 or more times
- ` ? ` - 0 or 1 time
- ` {5} ` - exactly 5 times
- ` {1.5} ` - from 1 to 5 times
- ` {1,} ` - from 1 time
- ` {,5} ` - up to 5 times

*For example:*

- ` a+ ` - corresponds to a, aa, aaa, etc.
- ` .* ` - corresponds to any text, even empty;
- ` ab{3} ` - abbb

**Groups**

Parentheses ( ) - allow you to combine characters into a group. Groups are most often used with quantitative symbols from the previous section, or with a vertical line symbol **\| ** which denotes a logical OR.

*For example:*

- ` ((Bob)|(Alice)) ` - corresponds to the lines of both *Bob* and *Alice*;
- (abc){3} - corresponds to *abcabcabc*;

**Character set**

Square brackets **\[ \]** are used to specify the character set, and characters can be listed inside them as follows:

- \[a-z\] - any Cyrillic character
- \[abvgd\] - any character *a,b,c,d* or *d* (the same as and \[a-d\])
- \[a-z\] - any Latin character
- \[0-5\] - any digit from 1 to 5

Inside square brackets, the symbol ^ means a logical NOT (negation symbol):

- \[^a-z\] - any character EXCEPT the Cyrillic character
- \[a-z\] - any character EXCEPT the Latin character
- \[^\\s\] - any NON-whitespace character

**Escaping characters**

If you want to use a service character simply as text, and not as part of the syntax of a regular expression, then it must be escaped using the backslash **\\ **.

*For example:*

- ` :\) ` - corresponds to the string *:)* (the bracket does not mean a group, but just a bracket);
- who\\? - corresponds to the line *who?* (the question mark in this case is not a quantitative symbol, but just a question mark)

## Ready-made templates

Below are ready-made regular expression templates that you can copy and use for your tasks:

- Any telegram username is ***@\[a-z0-9\_\]{4,}***
- Any link is ***https?:\\/\\/\[^\\s\]\****

The list will be expanded later, to add new ones, write to support [@value\_maker](<https://t.me/value_maker>). To test your own controls, use the site [regexp.com](<https://regex101.com>).