How to Use STRLEN Command in Redis for String Length

Use the STRLEN command in Redis to get the length of the string stored at a specific key. It returns the number of bytes of the string value or 0 if the key does not exist.

Syntax

The STRLEN command syntax is simple:

• STRLEN key: Returns the length of the string value stored at key.

If the key does not exist, it returns 0. If the key holds a non-string type, it returns an error.

redis

STRLEN mykey

Example

This example shows how to set a string value and then get its length using STRLEN:

redis

SET greeting "Hello, Redis!"
STRLEN greeting

Output

13

Common Pitfalls

Common mistakes when using STRLEN include:

• Trying to get length of a key that does not exist returns 0, which might be confused with an empty string.
• Using STRLEN on keys holding non-string types causes an error.
• Remember that STRLEN counts bytes, so multibyte characters count as multiple bytes.

redis

/* Wrong: Using STRLEN on a list key */
LPUSH mylist "item1"
STRLEN mylist

/* Right: Use STRLEN only on string keys */
SET mystring "abc"
STRLEN mystring

Output

(error) WRONGTYPE Operation against a key holding the wrong kind of value
3

Quick Reference

Command	Description
STRLEN key	Returns the length of the string stored at key
Returns 0	If key does not exist
Error	If key holds a non-string type

Key Takeaways

Use STRLEN to get the byte length of a string stored at a Redis key.

STRLEN returns 0 if the key does not exist, not an error.

Do not use STRLEN on keys holding non-string types to avoid errors.

STRLEN counts bytes, so multibyte characters increase length accordingly.