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MacOS Quicklook plugin for gtf and gff3 files?

Does anyone know of any MacOS Quicklook plugins that can handle gtf and/or gff3 files? Google searches are turning up nothing.

gtf gff3 macos
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written by kalavattam • kalavattam

These are text format files so why do you need a plugin?

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written by GenoMax GenoMax

Because of their extensions, they seem to not be handled by vanilla Quicklook.

But maybe I don't need a plugin? I'm looking for a quick way to peruse the contents of gtf and gff3 files that I'm writing.

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written by kalavattam • kalavattam

head in your shell terminal?

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written by Meisam • Meisam

Yeah, this'll work, although it's not ideal for my use case with very large numbers of files, e.g.,

find ./path/etc/ -type f -name "*.gtf" -exec head -20 {} +
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written by kalavattam • kalavattam

What do you want to do with this functionality? If we are talking about the same quicklook then that is simply a way of looking inside a file. You could also highlight file(s) --> "right click" --> "Open with" --> "TextEdit" to get more or less the same experience.

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written by GenoMax GenoMax

Sorry if I was not clear, I was looking for a way to be able to press the space bar to have a Quicklook window open, which would allow a user to quickly see the initial contents of the file. With Quicklook open, the user can use the up and down arrows to quickly view the contents of other gtf/gff3 files in the directory. At least on my system with OS Ventura 13.0.1, your suggestion doesn't facilitate that.

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written by kalavattam • kalavattam

Change the Finder association so the files are opened with TextWrangler or BBEdit. Preview should then show content for moderately sized files at least.

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written by Ram Ram

3 answers

I came across this: https://www.addictivetips.com/mac-os/add-quicklook-support-for-text-based-files-on-macos/ Sounds like it may work in your case. You can decide if you want to try it out.

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written by GenoMax GenoMax

Thanks, yes, installing and running QLStephen ultimately works well. However, I found that getting the plugin to run properly and recognize gtf and gff3 files was a bit tricky. If anyone reading this encounters issues, here are some links for troubleshooting that I found helpful:

Regarding the last two points, you need to follow the steps in relevant comment #1 to obtain a value to be included in Info.plist as described in relevant comment #2.

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written by kalavattam • kalavattam

To recap, QLStephen was a suggested solution to solve an issue on macOS systems where standard genomics text files (e.g., .bedGraph, .gtf, .fasta, etc.) are recognized as generic public.data UTIs and not as file types that conform to public.plain-text. What does this mean? It means even though they are plain text files, they are not recognized and previewed as such by macOS Quick Look.

However, in 2026, using QLStephen is no longer viable. Given all the macOS updates and security changes since the initial answer, the QLStephen devs have chosen not to modernize the program.

So, I troubleshot this for a while with OpenAI GPT-5.5 and ended up with a different approach: a small, local, custom macOS app bundle that declares common genomics text-file extensions as UTIs that conform to public.plain-text. That, in turn, routes Quick Look to a text previewer so it can show a snippet of the file contents.

Per the comments above, it appears not all macOS systems seem to have this issue, but for those that do, and for anyone else interested, feel free to check out the GitHub Gist here. It’s a mix of AI-generated code and writing, and my human code and writing.

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written by kalavattam • kalavattam

You just need to tell MacOS to associate those extensions with a text editor.

Find one of the files in Finder -> Press Cmd + I and go to the "Open with" box -> Choose TextEdit (or you preferred app) -> Hit "Change all" to make that the default app for those extensions

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written by Joe Joe

You will need to repeat the process with every extension just FYI.

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written by Joe Joe

In my experience, this does not work. For example, I have my system set up to open gtf and gff3 files with text editor Sublime Text. When I space-bar a gtf or gff3 file via Finder, Quicklook shows me a small window with the name of the file and a Sublime Text graphic—but it does not show the contents of the file.

However, does this work for you? If so, can you post a screenshot of being able to space-bar over a gtf file and see the contents?

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written by kalavattam • kalavattam

I don't believe this will work with many 3rd party apps, but works with textedit.

I don't have a GTF or GFF3 to hand, but it should work the same as a genbank, so see below.

enter image description here

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written by Joe Joe

Thanks, Joe — I will download a genbank file later and play around with it and some gtf/gff3 files on my other system, which has an unmodified QuickLook. I'll see if I can get QuickLook previews working without the need to install QLStephen.

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written by kalavattam • kalavattam

For what it's worth, the suggestion given by GenoMax, which is to install and run the QuickLook plugin QLStephen, does work.

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written by kalavattam • kalavattam

Thanks for confirming that. I moved my comment to an answer to provide closure to this thread.

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written by GenoMax GenoMax

I've marked your post as an answer.

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written by kalavattam • kalavattam

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