How to install, change, and customize WordPress themes

Short answer: there are three ways to install a WordPress theme. From the WordPress theme repository (Appearance > Themes > Add New Theme – works for any free theme on wordpress.org). From a zip file (Appearance > Themes > Add New Theme > Upload Theme – works for premium themes from Astra, GeneratePress, Divi, ThemeForest, etc.). Or by uploading the unzipped theme folder directly into wp-content/themes/ through your hosting control panel’s file manager or SFTP, and activating from the dashboard. The repository method is fastest, the zip upload is for premium themes, and the file manager / SFTP method is the fallback when a zip upload fails because the file is too large for your server’s upload limit.

Your WordPress theme controls the entire visual layer of your site – layout, typography, colors, header, footer, and how content is structured on every page. Installing a new WordPress theme, switching between themes, uploading a theme to WordPress from a zip file, or customizing what you already have are among the most common tasks in WordPress. Picking and installing a theme is typically the first thing people do right after WordPress itself is installed. Here is how to do all of them without breaking your site.

How to install a WordPress theme: methods at a glance#

The first two methods cover roughly 95% of cases. The dashboard handles both for you. The file manager / SFTP method exists because zip uploads sometimes fail on shared hosting where the PHP upload limit is set lower than the theme file size, and the WP-CLI method exists for anyone managing multiple sites or scripting deployments. All four end with the same dashboard step: clicking Activate on the installed theme.

Installing a theme#

There are two ways to install a WordPress theme through the dashboard: from the official repository, or by uploading a zip file. A third way – through the hosting control panel file manager or SFTP – covers the edge case where a zip upload fails.

From the WordPress theme repository#

1. Go to Appearance > Themes in your WordPress admin.
2. Click Add New Theme at the top.
3. Browse or search for a theme by name, feature, or layout type.
4. Hover over the theme and click Install.
5. Once installed, click Activate to make it your active theme.

The WordPress theme repository only lists free themes that have passed a review process. This does not guarantee quality or long-term maintenance, but it does mean the theme met basic coding standards at the time of submission. If you are picking a theme primarily for SEO reasons, WordPress SEO tips for small businesses covers why “best SEO theme” is mostly a marketing label and which lightweight themes (GeneratePress, Astra, Kadence, Blocksy) actually deliver the underlying speed and clean HTML that helps rankings.

Uploading a zip file#

Premium themes from developers like Astra Pro, GeneratePress, Divi, or Flavor are distributed as zip files. So are themes purchased from marketplaces like ThemeForest.

1. Go to Appearance > Themes.
2. Click Add New Theme, then Upload Theme.
3. Choose the zip file from your computer and click Install Now.
4. Once the upload finishes, click Activate.

If the upload fails with an error about the file being too large, your server’s upload limit is lower than the theme file size. This is the same 413 Request Entity Too Large error that occurs with any oversized upload. The fix is either to raise the upload limit or to install the theme through the hosting file manager or SFTP instead.

Uploading a theme via the file manager or SFTP#

When the dashboard zip upload fails or you are working with a large premium theme bundle, you can install the theme by placing the unzipped folder directly into the themes directory. The fastest way is your hosting control panel file manager (no external client required); SFTP or FTPS works too if you prefer a dedicated client.

1. Unzip the theme file on your computer. You should get a folder named after the theme (e.g. astra-pro/ or Divi/ ) containing PHP, CSS, and template files.
2. Open the hosting control panel file manager or connect to your site via SFTP or FTPS.
3. Navigate to wp-content/themes/ in your WordPress installation.
4. Upload the entire unzipped theme folder into wp-content/themes/ . Many control panel file managers also let you upload the original zip and extract it in place, which skips the local unzip step.
5. Once the upload finishes, go to Appearance > Themes in your WordPress admin. The new theme will appear in the list – click Activate.

The wp-content/themes/ directory is where all installed themes live on disk, whether active or not. For a detailed look at what this directory contains and why inactive themes matter for security, see what is wp-content and what goes in it.

Switching themes#

Switching themes means activating a different installed theme. Go to Appearance > Themes, hover over the theme you want, and click Activate. The change is instant and affects the entire site.

What survives a theme switch#

Your content is safe. Posts, pages, media, menus (the items themselves), widgets (the content), and all plugin functionality carry over. The database stores your content independently from the theme – that separation is fundamental to how WordPress works as a CMS.

What does not survive#

Theme-specific features disappear. This includes:

• Custom template layouts – if the old theme had custom page templates (full-width, sidebar-left, landing page), pages assigned to those templates revert to the new theme’s default layout.
• Theme-dependent shortcodes – some themes register their own shortcodes. After switching, those shortcodes render as plain text.
• Widget areas – if the new theme has different widget areas (sidebars, footers), widgets may be moved to the Inactive Widgets section.
• Customizer settings – colors, fonts, header images, and other settings configured through the Customizer are theme-specific. They are saved in the database (so switching back restores them), but they do not transfer to a different theme.
• Menu locations – menu items are preserved, but menu locations (Primary, Footer, etc.) are defined by the theme. After switching, reassign menus under Appearance > Menus or in the Customizer. See how to add and manage menus for the full walkthrough.

Before you switch#

1. Check the new theme on a staging site first. Activate it on a copy of your site to see what breaks before doing it in production. If your host offers staging environments, use them.
2. Note your current Customizer settings. Screenshot them or write them down. If you ever switch back, the settings will still be in the database, but if you are moving forward with a new theme permanently, you will need to reconfigure these.
3. Check plugin compatibility. Page builder plugins (Elementor, Beaver Builder, Divi Builder) store layouts in post meta, not in the theme. Switching themes usually preserves builder layouts, but the visual result can look different because the theme’s CSS no longer applies.

Updating a theme#

Theme updates work like plugin updates. Go to Appearance > Themes, and if an update is available, you will see a notification. Click Update to install the new version.

For themes installed from the WordPress repository, updates appear automatically. For premium themes installed via zip file, updates are handled differently depending on the developer:

• Some premium themes include a license key that enables automatic update checks through the dashboard.
• Others require you to download the new zip from the developer’s site and upload it manually (the same way you installed it).
• A few use a companion plugin to manage updates.

Updates overwrite the theme’s files entirely. Any changes you made directly to the theme’s PHP, CSS, or template files will be lost. This is why child themes exist.

Child themes vs parent themes#

A child theme inherits everything from a parent theme and lets you override specific parts without modifying the parent. When WordPress renders a page, it checks the child theme first and falls back to the parent for anything the child does not override. If you want to go beyond child themes and build a custom theme from scratch, that guide covers the template hierarchy, functions.php , block themes, and custom post types.

Why child themes matter#

If you customize a theme by editing its files directly, the next theme update will overwrite every change you made. A child theme avoids this because the parent updates independently while your customizations remain in the child theme’s directory.

Creating a child theme#

A child theme needs only two files at minimum:

style.css with a required header:

/*
Theme Name: Your Theme Child
Template: your-theme
*/

The Template line must match the parent theme’s directory name exactly. Not the display name – the folder name in wp-content/themes/ .

functions.php to load the parent theme’s styles:

<?php
add_action('wp_enqueue_scripts', function() {
    wp_enqueue_style('parent-style', get_template_directory_uri() . '/style.css');
});

Place both files in a new directory inside wp-content/themes/ (for example, your-theme-child/ ). Then activate the child theme through Appearance > Themes. It will appear as a separate theme.

What you can override in a child theme#

• Template files – copy any template file from the parent (like header.php , single.php , page.php ) into the child theme directory and modify it. WordPress will use the child’s version.
• Styles – add custom CSS in the child theme’s style.css . It loads after the parent styles, so your rules take precedence.
• Functions – add new functions or override parent functions (if the parent uses function_exists() checks) in the child’s functions.php .
• Template parts – same as template files. Copy the specific part you want to change.

You do not need to copy every file from the parent. Only copy and modify the files you want to change. The fewer files in your child theme, the easier it is to maintain.

Customizing a theme without editing files#

WordPress provides several ways to customize your theme’s appearance without touching any code.

The Customizer (classic themes)#

Go to Appearance > Customize. The Customizer lets you change settings like:

• Site identity (title, tagline, logo, favicon) – this is the same site title and tagline that appears in browser tabs and search results, and the same panel where you upload the favicon / site icon
• Colors and typography (depends on the theme – if your theme does not expose font size controls here, how to change the font size in WordPress covers the CSS and theme.json paths that work on any theme, and how to change the font color in WordPress covers the equivalent paths for recoloring text, links, and headings)
• Header and background images
• Menu locations
• Widget placement
• Homepage settings (latest posts vs static page) – the same selector from Settings > Reading for configuring the homepage

Changes preview in real-time before you publish them. What is available in the Customizer depends entirely on the theme – premium themes typically expose more options.

The Full Site Editor (block themes)#

Block themes (like Twenty Twenty-Four and Twenty Twenty-Five) use the Full Site Editor instead of the Customizer. Go to Appearance > Editor to access it.

The Full Site Editor lets you modify:

• Templates – the layout structure of specific page types (single post, archive, 404, search results). Each template is built from blocks that you can rearrange, add, or remove.
• Template parts – reusable sections like headers and footers that are shared across templates.
• Global styles – fonts, colors, spacing, and layout defaults that apply across the entire site. This replaces the theme’s style.css for design tokens.
• Patterns – pre-designed block arrangements you can insert into pages and templates.

Block themes represent a different model from classic themes. Instead of PHP template files that mix logic and markup, block themes use HTML-based templates and a theme.json file that defines design options declaratively. Customization happens through the editor interface, and you rarely need to touch code. Typography in particular is handled differently – how to add custom fonts to WordPress walks through both the classic-theme Customizer approach and the block-theme theme.json / Font Library workflow.

Custom CSS#

For targeted visual changes that the Customizer or Site Editor do not cover, add custom CSS:

• Classic themes: Appearance > Customize > Additional CSS
• Block themes: Appearance > Editor > Styles > Additional CSS (click the three-dot menu in the Styles panel)

Custom CSS persists across theme updates because it is stored in the database, not in the theme files. It is a safe way to make small visual tweaks without a child theme – a common use case is hiding the theme’s automatic page title on specific pages when a page builder or hero design renders its own heading. For the full picture of when Additional CSS is the right choice versus moving to a child theme, and how to write rules that override the theme’s defaults cleanly, see how to edit and add custom CSS in WordPress. The Customizer’s Additional CSS and the Site Editor’s Styles only affect the live site – to make the editor canvas itself match while writing, see how to add custom styles to the WordPress visual editor.

The Twenty Twenty-Four "no top bar" problem#

Twenty Twenty-Four is a block theme, and it handles navigation differently from classic themes. If your pages are missing the top navigation bar or header, the issue is almost always the template structure.

1. Go to Appearance > Editor.
2. Click Templates in the left sidebar.
3. Select the template for the affected page type (usually Page or Single Posts).
4. Check if the template includes a Header template part at the top. If it is missing, add it.
5. If the header exists but looks wrong, click Template Parts in the sidebar, then edit the Header part directly.

The same applies to the footer. Block themes assemble pages from template parts, so a missing header or footer means the template is not including that part. This is not a bug – it is how block themes are designed to work. For the full walkthrough of the Footer template part – including how to remove the “Powered by WordPress” line and how the process differs between block themes, classic themes, and page builders – see how to edit the footer in WordPress.

Deactivating and deleting a theme safely#

Deactivating#

You cannot deactivate a theme the way you deactivate a plugin. WordPress always needs an active theme. To “deactivate” a theme, activate a different one. The old theme remains installed but inactive.

Deleting#

Inactive themes take up disk space, and more importantly, they are a security risk. An inactive theme’s PHP files are still on disk and some can be accessed via URL. If that theme has a known vulnerability, an attacker can exploit it even though it is not active. This is the same principle that makes outdated plugins dangerous – the code exists on the server whether it is running or not.

To delete an inactive theme:

1. Go to Appearance > Themes.
2. Click on the inactive theme to open its details.
3. Click Delete in the bottom-right corner.

Keep your active theme, its parent theme (if you are using a child theme), and one default theme as a fallback. Delete everything else.

The fallback theme matters because if your active theme crashes – say, after a PHP update makes it incompatible with a newer version – WordPress automatically falls back to the latest default theme installed. If no default theme exists, you get a white screen with no automatic recovery path.

Switching a theme via WP-CLI#

If you have SSH access, WP-CLI is the fastest way to manage themes:

# List installed themes
wp theme list

# Install a theme from the repository
wp theme install flavor --activate

# Activate an already-installed theme
wp theme activate flavor

# Update a theme
wp theme update flavor

# Update all themes
wp theme update --all

# Delete an inactive theme
wp theme delete flavor

WP-CLI is especially useful when the admin dashboard is inaccessible. If a theme update caused a white screen of death, you can switch to a default theme over SSH without needing the browser.

Choosing a theme#

This article focuses on the how, not the which – but a few practical guidelines:

• Lightweight beats feature-rich. A theme that loads 400KB of CSS and JavaScript on every page slows your site regardless of hosting. Starter themes like Flavor, Astra, GeneratePress, and Kadence load a fraction of that. The performance difference is measurable in Core Web Vitals scores.
• Check the last update date. A theme that has not been updated in two years may not support the current WordPress version, the current PHP version, or the Full Site Editor. An abandoned theme is a liability.
• Block theme vs classic theme. Block themes are the direction WordPress is heading. They use the Full Site Editor and theme.json for customization. Classic themes use the Customizer and PHP templates. Both work, but new sites benefit from starting with a block theme since the tooling and community investment is moving that way.
• Check the reviews and active installations. A theme with 500,000 active installations and a 4.8 rating is a safer bet than one with 200 installations and no reviews. Popular themes get more bug reports, more patches, and more community resources.

If you are migrating an existing site to a new host and want to bring your theme along, see how to migrate WordPress to another hosting provider for the complete process including theme files.