12 Tips to Build Your First WordPress Theme (Block Themes, 2026)

Want to build your first WordPress theme? Guest author Sandip Dedhia spent 20 days on his first theme in 2008 and shared the lessons that would have saved him time. Theme building has changed a lot since then: block themes use HTML templates and a theme.json file instead of lots of PHP, and you can design much of a theme visually in the Site Editor. Here are 12 essential tips to build your first WordPress theme in 2026.

Quick answer: Start from a default block theme such as Twenty Twenty-Five, or use the free Create Block Theme plugin to export your Site Editor design as a new theme. Set colours, fonts and spacing in theme.json, build templates from blocks and patterns, work on a fresh local WordPress install, never hard-code URLs, and test with Theme Check and accessibility tools before sharing it.

Block theme or classic theme?

• Block themes (recommended): templates are HTML files made of blocks, global styles live in theme.json, and users can customise everything in the Site Editor.
• Classic themes: PHP templates like index.php and single.php. Still supported, and fine if you prefer PHP or need to customise an existing classic theme.

12 tips for your first WordPress theme

1. Don’t start from scratch. Copy a default theme or use the Create Block Theme plugin to generate a starter theme from the Site Editor.
2. Consider a child theme if you only want to change an existing theme; your changes survive parent updates.
3. Use a fresh, local WordPress install. Sandip lost days because his old test blog had edited core files. Tools like WordPress Studio or LocalWP give you a clean site in minutes.
4. Get the essentials right. A block theme needs style.css (with the theme header), theme.json and templates/index.html. A classic theme needs style.css and index.php.
5. Put design settings in theme.json: colour palette, font sizes, spacing and layout widths. It keeps styles consistent and editable.
6. Build with patterns and template parts. Reusable headers, footers and sections keep code modular and save time.
7. Never hard-code URLs, paths or text. Use functions like get_theme_file_uri() and make text translatable if you plan to share the theme.
8. Turn on debugging. Set WP_DEBUG to true in a local site to catch errors and deprecated functions early.
9. Avoid deprecated code copied from old tutorials; check the official handbook for current functions.
10. Keep it lean. Fewer scripts, fonts and database calls mean a faster theme. Load only what each page needs.
11. Test thoroughly with the Theme Unit Test data, the Theme Check plugin, different screen sizes and keyboard navigation.
12. Ask for help. The Theme Handbook and WordPress support forums are excellent.

You don’t need to be a PHP expert

With block themes, much of the work is HTML, CSS and JSON, and the Site Editor lets you design visually. Sandip’s advice still holds: start small, reuse good code, and learn as you go. We built several free classic themes for QuickOnlineTips years ago. One lesson from that: never add footer links back to your site in themes you give away, as those links later looked like spam and hurt our rankings.

When your theme is ready, keep it fast: see how to make WordPress faster and safer and the essential web design elements every theme needs.

FAQ

How long does it take to build a WordPress theme?

A simple block theme can take a weekend; a polished, public theme takes weeks of testing.

Can I sell my WordPress theme?

Yes, but themes must be GPL-compatible. To list it on WordPress.org it must pass the theme review requirements.

What is theme.json?

A configuration file that defines a theme’s colours, typography, spacing and which editor features are available.

Originally written by guest author Sandip Dedhia of BlogsDNA, who blogged about technology, Linux and blogging tips. Updated for 2026 by QuickOnlineTips.