MySQL utf8 vs utf8mb4: what is the difference between utf8 and utf8mb4?
When working with MySQL databases, you may encounter utf8 and utf8mb4 character encodings, which at first glance may seem similar. However, they have significant differences that can affect data storage and display, especially when dealing with different characters and emojis. Understanding the differences between utf8 and utf8mb4 is critical to choosing the right character set for your database and ensuring your data is stored correctly.
In this article, we will look at the differences between utf8 and utf8mb4 in MySQL, the reasons for utf8mb4, and how to migrate your database to utf8mb4 if necessary.
What is utf8 in MySQL?
In MySQL, the utf8 character set has historically been used to store Unicode data. It was designed to support all Unicode characters, making it suitable for most text data, including many languages and special characters. However, MySQL’s implementation of utf8 supports only a subset of the full UTF-8 standard.
How many bytes does utf8 use?
The utf8 character set in MySQL encodes characters using between 1 and 3 bytes per character. This means that it cannot represent characters that require 4 bytes, such as some emojis and some less common Chinese, Japanese, and Korean (CJK) characters. If you try to store such 4-byte characters in a utf8 column, MySQL will return an error, causing data insertion to fail.
Example of unsupported characters in utf8:
- Emoji such as 😊, 🚀, and ❤️.
- Some rare CJK characters.
- Mathematical symbols and other specialized Unicode characters.
This limitation led to the implementation of utf8mb4 in MySQL.
What is utf8mb4 in MySQL?
The utf8mb4 character set in MySQL is a true implementation of the full UTF-8 standard. It supports 1 to 4 bytes per character, allowing the entire Unicode character set to be used. This includes all characters that utf8 supports, as well as additional 4-byte characters that utf8 does not support.
Why was utf8mb4 introduced?
MySQL introduced utf8mb4 to address the shortcomings of utf8. With utf8mb4, you can store any valid Unicode character, including emoji, musical notes, math symbols, and the entire CJK character set. This makes utf8mb4 the preferred character set for modern applications that need to support a wide range of text data.
Main differences between utf8 and utf8mb4
| Characteristic | utf8 | utf8mb4 |
| Bytes per character | 1-3 | 1-4 |
| Unicode coverage | Partial (excludes 4-byte characters) | Full (supports all Unicode) |
| Emoji support | No | Yes |
| CJK characters | Most, but not all | All |
| Compatibility | Outdated databases | Recommended for new projects |
1. Byte length
The most significant difference between utf8 and utf8mb4 is the number of bytes used to store characters. utf8 supports up to 3 bytes, while utf8mb4 supports up to 4 bytes. As a result, utf8mb4 can store a wider range of Unicode characters.
2. Emoji and special characters
If you need to store emoji or any special characters that require 4 bytes, utf8mb4 is the only viable option. With utf8, attempting to store a 4-byte character will result in an error, which can cause data loss or application crashes.
3. Database Compatibility
utf8 was the default character set for many older MySQL installations, making it compatible with legacy systems. However, for new projects and applications that need to support a global audience with different character sets, utf8mb4 is now recommended.
Why use utf8mb4 instead of utf8?
Given the limitations of utf8, using utf8mb4 is generally a better choice for modern applications. Here are a few reasons to prefer utf8mb4:
- Full Unicode support: utf8mb4 allows you to store all Unicode characters, including emojis, which are becoming increasingly common in user-generated content.
- Persistence: As new characters are added to the Unicode standard, utf8mb4 ensures that your database can handle them.
- Global Compatibility: With utf8mb4, you don’t have to worry about character set compatibility for different languages and special characters.
When should I still use utf8?
There are a few scenarios where utf8 should still be used:
- Data storage space: Since utf8mb4 uses up to 4 bytes per character, this can result in a slightly larger database size than utf8. However, for most applications this difference is often negligible.
- Legacy systems: If you have an existing application or database that uses utf8 and you do not need to store 4-byte characters, switching may not be necessary.
How to convert a database from utf8 to utf8mb4
If you decide to convert an existing MySQL database from utf8 to utf8mb4, it involves several steps to ensure a smooth transition. Here is a general guide on how to convert a database to utf8mb4.
Step 1: Backup the database
Before making any changes, always back up your database to prevent data loss:
mysqldump -u username -p database_name > database_backup.sql
Step 2: Change the character set and collation
Run the following SQL commands to change the character set and collation of your database, tables and columns to utf8mb4:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;
For each table, run the command:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
This will change the character set and collation for the specified table and its columns.
Step 3: Update the configuration file
To make the new tables and columns use utf8mb4 by default, update the MySQL configuration file (my.cnf or my.ini) with the following settings:
[client]
default-character-set = utf8mb4
[mysql] default-character-set = utf8mb4
[mysqld]
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
Restart MySQL to apply the changes:
sudo service mysql restart
Step 4: Check the changes
Verify that the character set has been successfully updated:
SHOW VARIABLES LIKE 'character_set%';
SHOW VARIABLES LIKE 'collation%';
As a result, you should see utf8mb4 as the character set for your database.
Conclusion
The choice between utf8 and utf8mb4 in MySQL can significantly affect the way you store data and the types of characters you can support. Although utf8 was widely used in older versions of MySQL, it is limited by the fact that it cannot store 4-byte characters such as emojis. On the other hand, utf8mb4 provides full Unicode support, making it a recommended option for new databases and applications that require support for a variety of characters and symbols.
By using utf8mb4, you ensure that your database is ready for modern text content, including emojis and complex multilingual characters. If you maintain an existing utf8 database, consider switching to utf8mb4 to protect your application in the future and avoid potential data storage issues.
By clearly understanding the differences between utf8 and utf8mb4, you will be able to make an informed decision and ensure that your MySQL databases meet the needs of your application and its users. Happy coding!
