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Doctype Inserter self-updates

Add simple source-code messages immediately after the HTML doctype in WordPress.

by Cem Firat · github.com/cemfirat/wordpress-doctype-inserter · website

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Install

No release zip yet. The repository archive installs, but the folder name will carry the branch suffix and updates will not flow:

wp plugin install https://github.com/cemfirat/wordpress-doctype-inserter/archive/refs/heads/main.zip

Ships its own WordPress updater (built-in updater), so new versions show up under Dashboard → Updates.

Readme github.com/cemfirat/wordpress-doctype-inserter ↗

A small, free WordPress plugin for personal messages in the page source. Add website credits, a developer greeting, a hiring note, or an advanced trusted snippet immediately after the HTML doctype.

Author: Cem Firat
License: GPL-2.0-or-later
Requirements: WordPress 5.8+ and PHP 7.4+.

What it does

Version 1.2 adds a Simple comment mode. Write normal text and Doctype Inserter creates the HTML comment for you:

<!DOCTYPE html>
<!--
Hello, developers!
We're hiring: https://example.com/jobs
-->
<html>

The message does not appear in the visible page layout. It is public to anyone who inspects the response or page source.

The settings screen includes a live source preview, templates for credits/hiring/developer greetings, an output toggle, and a home-page output check for spotting cache or minification issues. The preview displays input as text and does not execute it. Simple mode preserves source-like text such as <html>, percent-encoded URLs, dollar signs, backslashes, line breaks and ordinary --. It only removes NUL bytes and neutralizes sequences that would conflict with HTML comment delimiters.

Backward compatibility

Existing 1.0/1.1 installations that already contain doctype_inserter_text automatically remain in Advanced snippet mode. Their saved snippet is not rewritten. New installations default to Simple comment mode.

Advanced mode remains available for trusted raw HTML/JavaScript and requires both manage_options and unfiltered_html. Simple comments require only manage_options.

Install

  1. Download doctype-inserter.zip from the latest release.
  2. In WordPress open Plugins → Add New → Upload Plugin, upload the ZIP, and activate it.
  3. Open Settings → Doctype Inserter.
  4. Write a message, save it, and inspect the page source.
  5. If needed, clear page/CDN caches or use Check home page output.

Version 1.0 has no updater. Install 1.1.0 or newer manually once; subsequent stable GitHub releases can then be discovered through WordPress.

Output behavior

Doctype Inserter only changes ordinary front-end HTML documents with a leading HTML doctype. Admin pages, feeds, REST, AJAX, cron, XML-RPC, WP-CLI, HEAD requests, robots.txt, favicons, redirects, downloads, encoded responses, and fixed Content-Length responses are skipped.

The output engine buffers only the document preamble (up to 64 KiB), then streams the remaining response. Pages without an eligible doctype are unchanged.

The Check home page output button performs an on-demand request from WordPress to the site's own home page and searches for the active message. Normal page rendering makes no network request.

Updates and privacy

Stable updates are delivered from this public GitHub repository using WordPress's Update URI integration. Update checks contact api.github.com; package downloads use github.com. No saved message or site content is sent to GitHub.

Development

Run:

php tests/run.php
python3 scripts/package.py

GitHub Actions also runs syntax checks and WordPress integration tests.

Copyright © 2026 Cem Firat. Doctype Inserter is licensed under GPL-2.0-or-later.