One of the deep mysteries to me is our logo, the symbol of lust and knowledge, bitten into, all crossed with the colors of the rainbow in the wrong order. You couldn’t dream a more appropriate logo: lust, knowledge, hope and anarchy.
— Jean-Louis Gassée
A logotype gives a programming language a unique look and feel that makes it instantly recognizable and easier to remember. It is more than just a nice design – it is a way for users to connect, feel part of a community, and rally around a shared symbol. The logo also says something about what the language stands for, helping people get a quick sense of its vibe. Plus, it is useful for spreading the word; a good logo can make the language more visible in tutorials, online discussions, and conferences, making it stick in people’s minds and building a legacy over time. Here are the logotypes for four well-established languages:
By contrast, there is no Prolog logo broadly recognized across the language’s subcommunities. Perhaps that absence says something. Maybe Prolog has long been content to appear as an academic language rather than a public-facing technology. But the world has changed. Even niche languages now tend to have a clear visual identity, because branding, recognizability, and community-building matter more than they once did, especially in open-source and web-facing settings. Prolog should not be the odd one out forever.
The good news is that we need not begin from scratch. The field of logic programming already possesses an emblematic resource: the white-on-black geometric symbol at the heart of the logo for the Association for Logic Programming (ALP):
Familiar to logicians, the three glyphs ⊨, ≡ and ⊢ stand for semantic entailment, logical equivalence and syntactic inference, respectively. Though underutilized and perhaps underrecognized, the equation expresses a core thesis of logic programming: that syntax and semantics, process and meaning, are formally intertwined. The equation, while not fully realized in practical Prolog, remains a guiding principle of logic programming – and a fitting philosophical emblem for Prolog. In the spirit of reuse and renewal, and adding a frame and a bit of color, I’d like to propose a Prolog logotype based on this symbol:
And once that basic idea is in place, it can easily be extended. Replace the name “Prolog” with the names of other logic programming languages, vary the colours, and you get a family of related logotypes for the broader logic programming world:
Of course, there is a catch. These logos need to look 2025-modern, not 1995-modern. A good concept is not enough if the rendering makes it look dated. So the mockups need professional polish if the idea is to be taken seriously. Still, it is interesting to see what happens when one lets ChatGPT take a first stab at the Prolog logo:
And here is what it did with the others:
Or perhaps a 1972-retro look suits us better? :-)
What do you think?