Title: How to install Headline Testing Author: Lucas Radke Published: June 16, 2025 Last modified: July 6, 2026 --- 1. [Installation resources](https://docs.parse.ly/installation-resources/) 2. [Add-on Features](https://docs.parse.ly/installation-resources/add-on-features/) 3. How to install Headline Testing # How to install Headline Testing This guide outlines the technical requirements and best practices for installing and customizing Parse.ly’s Headline Testing feature. Proper installation ensures headline variants load efficiently and tests perform reliably across all supported browsers and platforms. ## Installation through the Parse.ly WordPress Plugin Headline Testing can be enabled and configured directly from the WordPress Admin area by using the [Parse.ly WordPress plugin](https://docs.parse.ly/installation-resources/installation-tools/wordpress-plugin/). This option allows for Headline Testing install without manually adding scripts or editing templates. Review the [Configure Headline Testing in the Parse.ly WordPress Plugin](https://docs.parse.ly/installation-resources/add-on-features/install-headline-testing/configure-headline-testing-in-the-parse-ly-wordpress-plugin/) guide. ## One-line snippet script installation Place this script in the **before** any other scripts but **after** all < meta /> tags: ```lang-html ``` Make sure to add your [Site ID](https://docs.parse.ly/site-id/) as the apiKey to the script’s source. This should be a domain-like value, such as example.com, and not your API Secret! Please ensure to test the script on your staging website first to ensure everything loads correctly and there are no errors in your browser console. Note that in the script above, we’re recommending that you enable the “live updates” [configuration option](https://docs.parse.ly/install-headline-testing/#3-configuration-options) by default. You can remove this option if you so choose. The script is approximately 9kB (gzipped) and is delivered via our global edge network. This implementation loads the script synchronously, ensuring experiments run as often as possible. To load the script asynchronously, add the `async` or `defer` attributes. However, note that experiments may run less frequently if the script executes **after** the first contentful paint. ## Advanced installation In the Advanced Installation method, you will directly run a block of inline JavaScript code/snippet, loaded in your webpage’s tag. This method offers more control over how the headline testing suite behaves and provides more configuration options. ```lang-html ``` ## Installation through tag manager We do not recommend installing the script using a tag manager. This method may introduce a delay in script execution which can lead to experiments running less often. ## Configuration options ### Flicker control If the script loads asynchronously, you may experience flickering as headlines are replaced. To minimize this, use the advanced installation method and enable flicker control, which hides the page body for up to 500ms. Note that this option is only available via the Advanced Installation technique: ```lang-js // Rest of advanced script e.loadVIPExp("XXXXXXXX",{ enableFlickerControl: true }) ``` ### Live updates By default, headlines are swapped during the initial page load. If your website loads articles dynamically, as is the case with [Single-Page Applications (SPA)](https://docs.parse.ly/installation-resources/parsely-integration/tracking-code-setup/single-page-application/), and you want headlines to be updated for newly added anchors, you can enable live updates. When live updates are enabled, the system watches the page after the initial swaps and automatically updates headlines for eligible anchors as new links appear. You can also configure how long this lasts – by default, we watch the page for 30 seconds. Example of how to enable live updates for 5 seconds using the One-Line Snippet: ```lang-html