Programming languages
- C
- C++
- Objective-C
- Swift
- PHP 7 and 8
- JavaScript + jQuery
- HTML5
- CSS3 + SASS
- GLSL
- Perl
- Python
- Ruby
- Java
- Processing and Processing.js
- TeX
- Graphviz
- Quartz Composer
- Vuo
Web frameworks
- Drupal 5, 6, 7, 8, 9, and 10 (including Composer, Twig, and Symfony)
- Discourse
- Wordpress
- Phabricator
- Jekyll
- TWiki
App frameworks
- Qt and QML (using Qt Creator)
- Cocoa (macOS, using Xcode)
- Cocoa Touch (iOS, using Xcode)
- LLVM
- OpenGL
- Metal (macOS)
Databases and other server software
- MySQL + MariaDB
- PostgreSQL
- Apache HTTPD
- Apache Solr + Lucene, including:
- faceted search
- Apache Tika PDF attachment search
- map/geographic search
- Apache Nutch crawling/spidering/indexing
- Puppet
- Docker + ddev
- Elasticsearch + Logstash + Kibana (ELK)
- Red Hat Enterprise Linux + CentOS
- SmartOS + Illumos + OpenSolaris
- SSO using CAS, OAuth2, OpenID Connect, and Keycloak
- LDAP
- Postfix (SMTP)
- Dovecot (IMAP)
- SpamAssassin
- Rspamd
- Git and Subversion
- GitLab development and self-hosting
- Nextcloud
Web/cloud services
- Xero API
- Amazon AWS EC2, S3, and CloudFront
- Amazon Product API
- BunnyCDN
- Google Login
- Google Analytics
- Google Maps API
- reCAPTCHA
- hCaptcha
- Leaflet & OpenStreetMap
- PayPal
- Stripe
- Authorize.Net
Automated testing, continuous integration, and packaging
- Jenkins
- GitLab CI
- Travis CI
- Behat + Mink + Selenium
- BackstopJS
- DrupalCI
- QTestLib
- CMake and CTest
- Conan
- macOS code-signing and notarization
Embedded systems