> For the complete documentation index, see [llms.txt](https://docs.toomuchmedia.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.toomuchmedia.com/setup/nats-version-history-and-compatibility.md).

# NATS Version History & Compatibility

Welcome to the NATS version history guide. This reference matrix outlines the evolution of NATS releases, tracking PHP compatibility, database support milestones, distribution methods, and the specific Git/CVS targets associated with each release.

**If you have any questions about your current NATS version or its compatibility, please submit a support ticket before making any changes.**

<table data-search="false"><thead><tr><th width="134">NATS Version</th><th width="159">PHP Compatibility</th><th width="319">PHP-Specific Release Tags (if applicable)</th><th width="124">Distribution</th><th width="233">MySQL Compatibility</th></tr></thead><tbody><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.1.2.34"><strong>5.1.2.34</strong></a></td><td>PHP 7.1.x - 8.3.x</td><td></td><td>Git</td><td>MySQL 5.7.8 – 8.4.3</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.1.2.7"><strong>5.1.2.7</strong></a></td><td>PHP 7.1.x – 8.2.x</td><td></td><td>Git</td><td>MySQL 5.7.8 – 8.4.3</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.1.1.4"><strong>5.1.1.4</strong></a></td><td>PHP 7.1.x – 8.2.x</td><td></td><td>Git</td><td>MySQL 5.7.8 – 8.0.32</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.1.1.1"><strong>5.1.1.1</strong></a></td><td>PHP 7.1.x – 8.1.x</td><td></td><td>Git</td><td>MySQL 5.7.8 – 8.0.32</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.0.4.4"><strong>5.0.4.4</strong></a></td><td>PHP 7.1.x – 8.1.x</td><td></td><td>Git</td><td>MySQL 5.1 – 8.0.32</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.0.4.1"><strong>5.0.4.1</strong></a></td><td>PHP 7.4.x – 8.1.x<br><br>PHP 7.1.x – 7.4.x</td><td><code>REL_NATS_5_0_4_1_PHP8</code><br><br><code>REL_NATS_5_0_4_1_PHP7</code></td><td>Git</td><td>MySQL 5.1 – 8.0.32</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.0.3.1"><strong>5.0.3.1</strong></a></td><td>PHP 5.6.x – 7.4.x</td><td><code>REL_NATS_5_0_3_1</code></td><td>Git</td><td>MySQL 5.1 – 5.7</td></tr><tr><td><a href="/pages/xZCD4NvTjclSVFLJ8Fs4#id-5.0.2.7"><strong>5.0.2.7</strong></a></td><td>PHP 5.6.x – 7.3.x<br><br>PHP 5.5.x – 5.6.x</td><td><code>REL_NATS_5_0_2_7</code><br><br><code>REL_NATS_5_0_2_7_PHP55</code></td><td>Git</td><td>MySQL 5.1 – 5.7</td></tr><tr><td><strong>5.0.0.1</strong></td><td>PHP 5.6.x – 7.3.x<br><br>PHP 5.5.x – 5.6.x</td><td><code>REL_NATS_5_0_0_1</code><br><br><code>REL_NATS_5_0_0_1_PHP55</code></td><td>Git</td><td>MySQL 5.1 – 5.7</td></tr><tr><td><strong>4.1.22.2</strong></td><td>PHP 5.6.x – 7.3.x<br><br>PHP 5.3.x – 5.6.x</td><td><code>REL_NATS_4_1_22_2</code><br><br><code>REL_NATS_4_1_22_2_PHP53</code></td><td>Git</td><td>MySQL 5.1 – 5.7</td></tr><tr><td><strong>4.1.22.1</strong></td><td>PHP 5.6.x – 7.3.x<br><br>PHP 5.3.x – 5.6.x</td><td><code>REL_NATS_4_1_22_1</code><br><br><code>REL_NATS_4_1_22_1_PHP53</code></td><td>CVS</td><td>MySQL 5.1 – 5.7</td></tr><tr><td><strong>4.1.21.1</strong></td><td>PHP 5.3.x – 5.6.x</td><td><code>REL_NATS_4_1_21_1</code></td><td>CVS</td><td>MySQL 5.1 – 5.6</td></tr><tr><td><strong>4.1.8.1</strong></td><td>PHP 5.2.x</td><td><code>REL_NATS_4_1_8_1_OLD_ENCODING</code></td><td>CVS</td><td>MySQL 5.1 – 5.6</td></tr></tbody></table>

## Smarty Template Engine Compatibility

NATS renders its admin, affiliate, member, and tour templates with the Smarty template engine. The Smarty version NATS uses is tied to your server's major PHP version:

| PHP Version | Smarty Version |
| ----------- | -------------- |
| PHP 7.x     | Smarty 2       |
| PHP 8.x     | Smarty 4       |

{% hint style="warning" %}
**Moving from PHP 7 to PHP 8?** Upgrading PHP also moves NATS from Smarty 2 to Smarty 4, and Smarty 4 is not backward-compatible with Smarty 2.

* Before upgrading PHP, [submit a support ticket](https://clients.toomuchmedia.com/) so we can make sure Smarty 4 is available for your NATS installation.
* If you use custom Smarty plugins, make sure they are PHP 8 compatible.
* Review your customized templates to make sure they still load as expected.

See [Upgrading from Smarty 2 to Smarty 4](/using-nats/one-off-articles/smarty/upgrading-from-smarty-2-to-smarty-4.md) for details.
{% endhint %}