More than a year ago my friend Thomas and I were looking for a good solution to digitally sign PDFs for NetzBeweis. However, we couldn't find a library that was easy to use and had a permissive open-source license so we could use it in a paid product. Sure, PDFbox would be an option, however, we didn't want to use a cannon to kill a fly. So we decided to create open-pdf-sign with the kind support of the Austrian internet foundation NetIdee.
After we were done, of course, we wanted people to use it. We asked a couple of friends, however, we realized that this was quite a specific product and we needed to get in touch with people outside our network.
Here is what we did
We posted on our own Linkedin accounts and Twitter. Launched on product hunt and did the obligatory "Show HN" post on the website HackerNews.
At the end of the day, we only had 17 stars on Github. We thought we had planted the seed, and over time more people would use it.
Then a friend had an idea, he said I should post on a news board for computing news, frequented by the open-source community. I posted our link there not expecting much. An hour later I checked our GitHub repository, and I saw that we had 70 stars. Frantically, I checked and refreshed the page, I thought this must be a bug or something.
What I found out only later is, that someone had 1:1 taken our post and put it on hacker news and we were on the front page.
This resulted in more than 10.000 page hits on our GitHub repository and hundreds of stars.
For people interested in graphs, this is what our star graph looks like.
However, the submission that got to the frontpage was posted by one the power users of HN with 100k+ karma. (See here) Also, he submitted the link to the GitHub repo directly, which might have made the difference.
Producthunt, while a good channel for product launches, might not have a technical enough audience for open source libraries.
In conclusion, there is no clear way to market your open source product, however, trying different channels and thinking hard how to reach your potential users might improve your odds of getting the attention your project deserves.