From Linux servers to Android phones, open source software is a critical part of our internet infrastructure and personal computing experience. This very website runs on Ghost (an open source publishing platform), Nginx (a free open-source, high-performance HTTP server) and Ubuntu Server (an open source operating system).
Since open source is integral part of the internet and online publishing, a very interesting topic to discuss is open source SEO software tools – especially since some of the biggest players in the field such as Moz, Ahrefs and SEMRush are all closed source proprietary platforms.
Categories of Open Source SEO Software
When it comes to SEO software in general, these are some of the most important categories in terms of functionality:
Category 1: Data-Oriented Tools
In this category I would include everything from keyword research tools to link analysis tools, site explorers and content explorers.
When it comes to the above mentioned there isn't any open source software that I know of, simply because these tools rely on proprietary datasets (and there isn't any open SEO data database).
Most of the proprietary tools in the space such as Moz and Ahrefs, use the dataset from Google Ads' keyword planner as their starting point, and enrich it with data from SEO APIs and clickstream data providers.
Also, many employ their own web crawlers (if I recall correctly Ahrefs' crawler is the second most active after Google) that usually power their backlink databases.
The situation is clear: We need Open Data for SEO.
Category 2: Website Tools
In this category I would include everything from website crawlers to website performance optimization tools, auditing tools, Chrome extensions and custom made scripts for SEO tasks automation. And when it comes to these there are indeed many great SEO tools:
Greenflare is a free and open source SEO analysis tool writen in Python and made by SEOs for digital marketing experts. You can use it to analyze and improve your on-page SEO, audit your server for issues, extract on-page info and more.
What I find a considerable advantage (compared for example to Screaming Frog freemium), is that there are no crawl limits whatsoever. Moreover, it has low hardware requirements (it's optimized to run on low-end machines with as little as 1 GB memory), and is compatible with Windows, MacOS and Linux.
You can download it directly from their website, or the grab the latest release and source code from Github. If you're a pythonista, you can also install Greenflare via pip.
pip install greenflare
Lighthouse is Google's open-source tool for auditing websites, with a focus on website performance. It offers automated audits and scoring for accessibility, SEO, and performance based on the Core Web Vitals. It is similar to Google's Pagespeed Insights (Google's hosted solution), with the difference that Lighthouse tests websites from your computer, using your internet connection.
The best part is that you can run it directly from Google Chrome in Chrome DevTools, or install is as a Chrome Plugin. You can find the source code of the project on GitHub.
SEO Macroscope is a website scanning tool for Windows that is free and open source. This tool focuses on finding broken links and scanning websites for common technical SEO issues. Some of its functionality overlaps with Screaming Frog, a very powerful and popular proprietary SEO spider, which is great news for simple checks of large websites (Screaming Frog's free edition is limited to crawling up to 500 URLs).
SEO Macroscope is available for MS Windows and the source code is also on GitHub.
Serposcope is free and open-source software that tracks rankings and monitors websites for issues. It's available for every operating system, and you can find the source code on GitHub.
Scrapy is a very powerful web scraper and crawler written in Python. You can use it to build your own SEO tools and apps, web spiders, and runs on Linux, Windows, Mac and BSD systems. It's free, open source and the source code is available on GitHub.
Category 3: Indie Tools & GitHub Repositories
As a last category of open source SEO software, I'd like to include the extensive code arsenal that is freely available on GitHub under open source licenses. A simple search for "SEO Tools" yields 600 code repositories at the time of writing, many of which are available under the open source MIT license.
There are many open source SEO tools but rather on the technical side of things, such as website crawlers, web spiders, rank trackers and website auditing tools.
A complete Moz-style SEO suite would require an extensive database of open SEO data, and nothing like this exists today; perhaps justifiable so, as it would be a very costly and technically challenging endeavor.
Not to be overlooked, there are many open source code repositories on GitHub that you can use in your SEO workflows or use for your own SEO software projects.
Last but not least, if you know of any great open source SEO tools that weren't included in this article, please let me know on Twitter.