Once in a while, clients say, "We found this great theme on Themeforest that does everything we want. It has a portfolio, 4 different sliders, SEO settings, and more!" What they don't know is they're in danger of theme lock-in.
Theme lock-in, AKA the theme lock-in effect, is being stuck with a theme because the theme controls the site's functionality, so the site would break without that theme.
For example, an engineering firm uses a theme's portfolio functionality to enter 30 detailed projects. Three years later they change the theme to give the site a facelift, and discover that all their projects have disappeared!
The problem arises from not realizing that in the WordPress world, functionality (how it works) belongs in plugins, and presentation (how it looks) belongs in themes.
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In the example above, the theme includes a custom post type for portfolio items. In addition to custom post types, lock-in themes often include other functionality, such as sliders, shortcodes, contact forms, SEO settings, and Google Analytics code. In such instances, changing the theme breaks the site, because data becomes inaccessible, shortcodes appear instead of rendering, Google Analytics stops tracking, etc.
To avoid theme lock-in, make sure functionality is handled by plugins, not the theme. You can keep plugins in place through multiple theme changes. In the example above, it'd be better to use a plugin to control the portfolio (a plugin from the Plugin Directory, or a custom plugin developed specifically for the site).
Avoid using the functionality in themes.Respect the very different roles of themes and plugins. Choose a theme for how it looks, not for its features. Of course, it's not quite as simple as finding a pretty theme; you should choose a theme that's well-coded, well-supported, and lightweight. We like Genesis and StudioPress themes.
If you simply must use the functionality in a theme, at least be aware of it so you can deal with it when the time comes to switch themes.
Now that you're aware of theme lock-in, avoid it and save yourself a lot of future pain. If you're preparing to build or revamp a WordPress site, contact us to see how we can help.
Featured image by David Goehring