MySQL 1071: Specified key was too long (Laravel migration) - Rocketeers app

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MySQL 1071: Specified key was too long (Laravel migration)
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### [\#Laravel](https://rocketeersapp.com/knowledge/laravel)

This migration error happens on older MySQL with the utf8mb4 charset, where indexed string columns exceed the index size limit. The fix is a one-line default in your service provider.

 Published by [Mark van Eijk](https://rocketeersapp.com/author/mark-van-eijk) on June 23, 2026 · 1 minute read

1. [About the error](#content-about-the-error)
2. [Why do I see this error](#content-why-do-i-see-this-error)
3. [Solution](#content-solution)
4. [Recommended: set a default string length](#content-recommended-set-a-default-string-length)
5. [Better long-term: upgrade MySQL](#content-better-long-term-upgrade-mysql)
6. [Per-column alternative](#content-per-column-alternative)

[\#](#content-about-the-error "Permalink")About the error
---------------------------------------------------------

Running `php artisan migrate` on a fresh install against older MySQL throws:

 ```
SQLSTATE[42000]: Syntax error or access violation: 1071
Specified key was too long; max key length is 767 bytes

```

It almost always fails on the `users` table when creating a unique index on the email or another `VARCHAR(255)` column.

[\#](#content-why-do-i-see-this-error "Permalink")Why do I see this error
-------------------------------------------------------------------------

Laravel defaults to the `utf8mb4` charset (proper 4-byte Unicode, needed for emoji and many scripts). In `utf8mb4` each character can take up to 4 bytes, so a `VARCHAR(255)` index needs `255 × 4 = 1020` bytes.

On **MySQL before 5.7.7** (and MariaDB before 10.2), the per-index limit without large-prefix support is **767 bytes**, less than 1020, so the index creation fails.

[\#](#content-solution "Permalink")Solution
-------------------------------------------

### [\#](#content-recommended-set-a-default-string-length "Permalink")Recommended: set a default string length

Laravel ships with a one-line fix. In `app/Providers/AppServiceProvider.php`, cap the default string length so indexed `VARCHAR` columns fit:

 ```
use Illuminate\Support\Facades\Schema;

public function boot(): void
{
    Schema::defaultStringLength(191);
}

```

`191 × 4 = 764` bytes, just under the 767 limit. Then re-run the migration:

 ```
php artisan migrate:fresh

```

### [\#](#content-better-long-term-upgrade-mysql "Permalink")Better long-term: upgrade MySQL

The 767-byte limit is a limitation of old versions. MySQL 5.7.7+ and 8.0 raise it to 3072 bytes with the InnoDB large prefix, and the error disappears without capping your column lengths. See [upgrading MySQL 5.7 to 8.0 on Ubuntu](/upgrade-mysql-5-7-to-8-0-ubuntu).

### [\#](#content-per-column-alternative "Permalink")Per-column alternative

If you only need it on a specific migration, set the length on the column directly instead of globally:

 ```
$table->string('email', 191)->unique();

```

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