How to fix “Incorrect string value” errors?

After noticing an application tended to discard random emails due to incorrect string value errors, I went though and switched many text columns to use the utf8 column charset and the default column collate (utf8_general_ci) so that it would accept them. This fixed most of the errors, and made the application stop getting sql errors when it hit non-latin emails, too.

Despite this, some of the emails are still causing the program to hit incorrect string value errrors: (Incorrect string value: 'xE4xC5xCCxC9xD3xD8...' for column 'contents' at row 1)

The contents column is a MEDIUMTEXT datatybe which uses the utf8 column charset and the utf8_general_ci column collate. There are no flags that I can toggle in this column.

Keeping in mind that I don’t want to touch or even look at the application source code unless absolutely necessary:

  • What is causing that error? (yes, I know the emails are full of random garbage, but I thought utf8 would be pretty permissive)
  • How can I fix it?
  • What are the likely effects of such a fix?

One thing I considered was switching to a utf8 varchar([some large number]) with the binary flag turned on, but I’m rather unfamiliar with MySQL, and have no idea if such a fix makes sense.


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

UPDATE to the below answer:

The time the question was asked, “UTF8” in MySQL meant utf8mb3. In the meantime, utf8mb4 was added, but to my knowledge MySQLs “UTF8” was not switched to mean utf8mb4.

That means, you’d need to specifically put “utf8mb4”, if you mean it (and you should use utf8mb4)

I’ll keep this here instead of just editing the answer, to make clear there is still a difference when saying “UTF8”


I would not suggest Richies answer, because you are screwing up the data inside the database. You would not fix your problem but try to “hide” it and not being able to perform essential database operations with the crapped data.

If you encounter this error either the data you are sending is not UTF-8 encoded, or your connection is not UTF-8. First, verify, that the data source (a file, …) really is UTF-8.

Then, check your database connection, you should do this after connecting:

SET NAMES 'utf8mb4';

Next, verify that the tables where the data is stored have the utf8mb4 character set:

  `information_schema`.`TABLES` AS `tables`,
  `information_schema`.`COLLATION_CHARACTER_SET_APPLICABILITY` AS `collations`
  `tables`.`table_schema` = DATABASE()
  AND `collations`.`collation_name` = `tables`.`table_collation`

Last, check your database settings:

mysql> show variables like '%colla%';
mysql> show variables like '%charac%';

If source, transport and destination are utf8mb4, your problem is gone;)

Method 2

MySQL’s utf-8 types are not actually proper utf-8 – it only uses up to three bytes per character and supports only the Basic Multilingual Plane (i.e. no Emoji, no astral plane, etc.).

If you need to store values from higher Unicode planes, you need the utf8mb4 encodings.

Method 3

The table and fields have the wrong encoding; however, you can convert them to UTF-8.



ALTER TABLE logtest CHANGE title title VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_general_ci;

Method 4

"xE4xC5xCCxC9xD3xD8" isn’t valid UTF-8. Tested using Python:

>>> "xE4xC5xCCxC9xD3xD8".decode("utf-8")
UnicodeDecodeError: 'utf8' codec can't decode bytes in position 0-2: invalid data

If you’re looking for a way to avoid decoding errors within the database, the cp1252 encoding (aka “Windows-1252” aka “Windows Western European”) is the most permissive encoding there is – every byte value is a valid code point.

Of course it’s not going to understand genuine UTF-8 any more, nor any other non-cp1252 encoding, but it sounds like you’re not too concerned about that?

Method 5

I solved this problem today by altering the column to ‘LONGBLOB’ type which stores raw bytes instead of UTF-8 characters.

The only disadvantage of doing this is that you have to take care of the encoding yourself. If one client of your application uses UTF-8 encoding and another uses CP1252, you may have your emails sent with incorrect characters. To avoid this, always use the same encoding (e.g. UTF-8) across all your applications.

Refer to this page for more details of the differences between TEXT/LONGTEXT and BLOB/LONGBLOB. There are also many other arguments on the web discussing these two.

Method 6

First check if your default_character_set_name is utf8.

SELECT default_character_set_name FROM information_schema.SCHEMATA S WHERE schema_name = "DBNAME";

If the result is not utf8 you must convert your database. At first you must save a dump.

To change the character set encoding to UTF-8 for all of the tables in the specified database, type the following command at the command line. Replace DBNAME with the database name:

mysql --database=DBNAME -B -N -e "SHOW TABLES" | awk '{print "SET foreign_key_checks = 0; ALTER TABLE", $1, "CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci; SET foreign_key_checks = 1; "}' | mysql --database=DBNAME

To change the character set encoding to UTF-8 for the database itself, type the following command at the mysql> prompt. Replace DBNAME with the database name:


You can now retry to to write utf8 character into your database. This solution help me when i try to upload 200000 row of csv file into my database.

Method 7

In general, this happens when you insert strings to columns with incompatible encoding/collation.

I got this error when I had TRIGGERs, which inherit server’s collation for some reason.
And mysql’s default is (at least on Ubuntu) latin-1 with swedish collation.
Even though I had database and all tables set to UTF-8, I had yet to set my.cnf:

/etc/mysql/my.cnf :


And this must list all triggers with utf8-*:


And some of variables listed by this should also have utf-8-* (no latin-1 or other encoding):

show variables like 'char%';

Method 8

Although your collation is set to utf8_general_ci, I suspect that the character encoding of the database, table or even column may be different.

ALTER TABLE tabale_name MODIFY COLUMN column_name VARCHAR(255)  
CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;

Method 9

I got a similar error (Incorrect string value: 'xD0xBExDOxB2. ...' for 'content' at row 1). I have tried to change character set of column to utf8mb4 and after that the error has changed to 'Data too long for column 'content' at row 1'.
It turned out that mysql shows me wrong error. I turned back character set of column to utf8 and changed type of the column to MEDIUMTEXT. After that the error disappeared.
I hope it helps someone.
By the way MariaDB in same case (I have tested the same INSERT there) just cut a text without error.

Method 10

That error means that either you have the string with incorrect encoding (e.g. you’re trying to enter ISO-8859-1 encoded string into UTF-8 encoded column), or the column does not support the data you’re trying to enter.

In practice, the latter problem is caused by MySQL UTF-8 implementation that only supports UNICODE characters that need 1-3 bytes when represented in UTF-8. See “Incorrect string value” when trying to insert UTF-8 into MySQL via JDBC? for details. The trick is to use column type utf8mb4 instead of type utf8 which doesn’t actually support all of UTF-8 despite the name. The former type is the correct type to use for all UTF-8 strings.

Method 11

In my case, Incorrect string value: 'xCCx88'..., the problem was that an o-umlaut was in its decomposed state. This question-and-answer helped me understand the difference between and ö. In PHP, the fix for me was to use PHP’s Normalizer library. E.g., Normalizer::normalize('o¨', Normalizer::FORM_C).

Method 12

The solution for me when running into this Incorrect string value: ‘xF8’ for column error using scriptcase was to be sure that my database is set up for utf8 general ci and so are my field collations. Then when I do my data import of a csv file I load the csv into UE Studio then save it formatted as utf8 and Voila! It works like a charm, 29000 records in there no errors. Previously I was trying to import an excel created csv.

Method 13

I have tried all of the above solutions (which all bring valid points), but nothing was working for me.

Until I found that my MySQL table field mappings in C# was using an incorrect type: MySqlDbType.Blob . I changed it to MySqlDbType.Text and now I can write all the UTF8 symbols I want!

p.s. My MySQL table field is of the “LongText” type. However, when I autogenerated the field mappings using MyGeneration software, it automatically set the field type as MySqlDbType.Blob in C#.

Interestingly, I have been using the MySqlDbType.Blob type with UTF8 characters for many months with no trouble, until one day I tried writing a string with some specific characters in it.

Hope this helps someone who is struggling to find a reason for the error.

Method 14

If you happen to process the value with some string function before saving, make sure the function can properly handle multibyte characters. String functions that cannot do that and are, say, attempting to truncate might split one of the single multibyte characters in the middle, and that can cause such string error situations.

In PHP for instance, you would need to switch from substr to mb_substr.

Method 15

I added binary before the column name and solve the charset error.

insert into tableA values(binary stringcolname1);

Method 16

Hi i also got this error when i use my online databases from godaddy server
i think it has the mysql version of 5.1 or more. but when i do from my localhost server (version 5.7) it was fine after that i created the table from local server and copied to the online server using mysql yog i think the problem is with character set

Screenshot Here

Method 17

To fix this error I upgraded my MySQL database to utf8mb4 which supports the full Unicode character set by following this detailed tutorial. I suggest going through it carefully, because there are quite a few gotchas (e.g. the index keys can become too large due to the new encodings after which you have to modify field types).

Method 18

There’s good answers in here. I’m just adding mine since I ran into the same error but it turned out to be a completely different problem. (Maybe on the surface the same, but a different root cause.)

For me the error happened for the following field:

@Column(nullable = false, columnDefinition = "VARCHAR(255)")
private URI consulUri;

This ends up being stored in the database as a binary serialization of the URI class. This didn’t raise any flags with unit testing (using H2) or CI/integration testing (using MariaDB4j), it blew up in our production-like setup. (Though, once the problem was understood, it was easy enough to see the wrong value in the MariaDB4j instance; it just didn’t blow up the test.) The solution was to build a custom type mapper:

package redacted;

import javax.persistence.AttributeConverter;

import static java.lang.String.format;

public class UriConverter implements AttributeConverter<URI, String> {
    public String convertToDatabaseColumn(URI attribute) {
        return attribute.toString();

    public URI convertToEntityAttribute(String field) {
        try {
            return new URI(field);
        catch (URISyntaxException e) {
            throw new RuntimeException(format("could not convert database field to URI: %s", field));

Used as follows:

@Column(nullable = false, columnDefinition = "VARCHAR(255)")
@Convert(converter = UriConverter.class)
private URI consulUri;

As far as Hibernate is involved, it seems it has a bunch of provided type mappers, including for, but not for (which is what we needed here).

Method 19

In my case that problem was solved by changing Mysql column encoding to ‘binary’ (data type will be changed automatically to VARBINARY). Probably I will not be able to filter or search with that column, but I’m no need for that.

Method 20

In my case ,first i’ve meet a ‘???’ in my website, then i check Mysql’s character set which is latin now ,so i change it into utf-8,then i restart my project ,then i got the same error with you , then i found that i forget to change the database’s charset and change into utf-8, boom,it worked.

Method 21

I tried almost every steps mentioned here. None worked. Downloaded mariadb. It worked. I know this is not a solution yet this might help somebody to identify the problem quickly or give a temporary solution.

Server version: 10.2.10-MariaDB - MariaDB Server
Protocol version: 10
Server charset: UTF-8 Unicode (utf8)

Method 22

1 – You have to declare in your connection the propertie of enconding UTF8.

2 – If you are using mysql commando line to execute a script, you have to use the flag, like:
Cmd: C:wamp64binmysqlmysql5.7.14binmysql.exe -h localhost -u root -P 3306 --default-character-set=utf8 omega_empresa_parametros_336 < C:wamp64wwwPontoEletronicoPE10002CorporacaoBancoDeDadosModeloomega_empresa_parametros.sql

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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