Craft 3 large log file sizes
Craft goes with Yii 2's defaults in the FileTarget class, which is 10MB for a log file before rotating. https://www.yiiframework.com/doc/api/2.0/yii-log-filetarget#$maxFileSize-detail

You can overwrite that behavior from your config/app.php file by using something like:

'components' =&gt; [
        'log' =&gt; function() {
            $log = Craft::createObject([
                'class' =&gt; yii\log\Dispatcher::class,
                'targets' =&gt; [
                    [
                        'class' =&gt; craft\log\FileTarget::class,
                        'levels' =&gt; !YII_DEBUG ? yii\log\Logger::LEVEL_ERROR | yii\log\Logger::LEVEL_WARNING : yii\log\Logger::LEVEL_ERROR | yii\log\Logger::LEVEL_WARNING | yii\log\Logger::LEVEL_INFO | yii\log\Logger::LEVEL_TRACE | yii\log\Logger::LEVEL_PROFILE,
                        'maxFileSize' =&gt; 5120, // 5MB
                    ],
                ],
            ]);

            return $log;
        },
    ],