# How to spot slow running extensions in Magento

> Use Magento's built-in Profiler to find extensions and SQL queries that are slowing down your store.

Source: https://www.kualo.com/knowledgebase/magento-performance/how-to-spot-slow-running-extensions-in-magento
Updated: 2026-06-09

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Magento's extensibility is one of its strengths, but poorly coded third-party extensions can seriously harm your site's performance. If your store is slow and otherwise well optimised, the Varien Profiler can help you pinpoint exactly what is causing the bottleneck.

## Quick check: disable unused extensions first

Before reaching for the Profiler, try disabling any modules or extensions you do not actively need. This is often the fastest way to recover performance without any code changes.

## About the Profiler

The Varien Profiler monitors the time and memory allocation of your application's loading cycle. It breaks down each block of code so you can see which extensions or queries are the slowest.

:::danger
Never run the Profiler on a live production site. It exposes detailed information about how your pages load and how your system is configured - information that could be exploited by anyone trying to compromise your store. Use it only in a development environment.
:::

## Enable the Profiler

1. In the Magento admin panel, go to **System > Configuration > Advanced > Developer > Debug**.
2. Set **Profiler** to **Yes**.

![Profiler setting in Magento admin](https://kb-cdn.kualo.com/d8/1b/d81bf118a87a32f9b1bf9ba711d1af146c91a3c2.png)

## Tell the Profiler what to monitor

With the Profiler switched on, you need to activate it in code. The simplest approach is to edit Magento's `index.php` file.

1. Open `index.php` in the root of your Magento installation.
2. Find the following line near the bottom of the file:

```php
#Varien_Profiler::enable();
```

3. Remove the `#` at the start to uncomment it:

```php
Varien_Profiler::enable();
```

4. Save the file.

## Read the Profiler output

Reload any Magento page and scroll to the bottom. You will see a **[Profiler]** link. Click it to expand a table of statistics.

![Profiler output table](https://kb-cdn.kualo.com/89/32/8932806f1b8854205a7140768b470cc4b6370ed5.png)

The table columns are:

| Column | What it shows |
|---|---|
| Code Profiler | The name of the timer or code block being measured |
| Time | How long that block of code took to execute |
| Cnt | How many times the timer with that name was started |
| Emalloc | Memory allocated to PHP, using `memory_get_usage()` without the `true` parameter, minus timer values |
| RealMem | Memory allocated to PHP, using `memory_get_usage(true)`, minus timer values |

Look for rows with a high **Time** value - these are your performance bottlenecks. Extension-related blocks will typically show their module name in the Code Profiler column.

## Enable SQL profiling

To see database query statistics alongside the standard output, open your Magento `local.xml` configuration file and add the following inside the connection node:

```xml
<profiler>true</profiler>
```

![SQL profiler setting in local.xml](https://kb-cdn.kualo.com/31/bf/31bf6cd4b0721ee8506fec2ff9094523a45e5852.png)

Reload a page and scroll to the bottom of the Profiler output. You will now see SQL query statistics alongside the standard code profiling data.

![SQL profiler output](https://kb-cdn.kualo.com/f6/71/f671e7e1e4741b50561e623b1a77fdb0754896b0.png)

If you need any further help, please [contact us](https://www.kualo.com/company/contact).

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_Source: Kualo Knowledgebase — https://www.kualo.com/knowledgebase/magento-performance/how-to-spot-slow-running-extensions-in-magento · © Kualo Ltd._