I've created a DigitalOcean droplet with "LAMP 18.04" preset and did all updates. Configured a new virtual host and used certbot to configure HTTPS. So far everything was working fine. Then I tried to enable HTTP2:

  • a2enmod http2
  • Added Protocols h2 http/1.1 to the HTTPS virtual host

However, browsers still use HTTP/1.1 when connecting to the site (with caching disabled). When running curl --http2 -v https://example.com (domain obfuscated) the following is printed:

* Connected to example.com ( port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* SSL connection using TLSv1.2 / ECDHE-RSA-CHACHA20-POLY1305
* ALPN, server accepted to use http/1.1

... And in headers:
< Upgrade: h2
< Connection: Upgrade

Furthermore, https://tools.keycdn.com/http2-test shows the following:

screenshot from HTTP2 testing tool

My question is - why is http/1.1 being chosen? Also, why does the tool think that HTTP2/ALPN is disabled? Here is the full VHost config:

<IfModule mod_ssl.c>
<VirtualHost *:443>
        ServerName example.com
        DocumentRoot /var/www/example/www
        Protocols h2 http/1.1

        ErrorLog ${APACHE_LOG_DIR}/example/error.log
        CustomLog ${APACHE_LOG_DIR}/example/access.log combined

        <IfModule mod_dir.c>
            DirectoryIndex index.php index.pl index.cgi index.html index.xhtml index.htm

        <FilesMatch "^index\.html$">
            Include no-cache.conf

Include /etc/letsencrypt/options-ssl-apache.conf
ServerAlias www.example.com
SSLCertificateFile /etc/letsencrypt/live/example.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/example.com/privkey.pem
  • You may want to ensure that you don't use the pre-fork MPM with HTTP/2
    – HBruijn
    Feb 14, 2019 at 9:26
  • Thanks, that helped! Turns out it was using mod_php by default with prefork - I've replaced it with mpm_event and php-fpm and now H2 works. Can you post that as answer so that I can accept it?
    – Xymanek
    Feb 14, 2019 at 10:00

1 Answer 1


Most distributions still default to the prefork MPM. (Unless you really have to use mod_php with really crappy ancient code there is no reason to do so anymore in this day and age.)

HTTP/2 support in Apache in combination with the prefork MPM comes with so many limitations that in practice it will deliver none of the benefits of HTTP/2. That is probably why with testing the headers indicate HTTP/2 and ALPN, offering h2 support but further testing shows a failure.

Switch to a different MPM and you should get HTTP/2 to actually work.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.