Why You Shouldn't Use Git LFS

May 12, 2021 at 10:30 AM | categories: Mercurial, Git

I have long held the opinion that you should avoid Git LFS if possible. Since people keeping asking me why, I figured I'd capture my thoughts in a blog post so I have something to refer them to.

Here are my reasons for not using Git LFS.

Git LFS is a Stop Gap Solution

Git LFS was developed outside the official Git project to fulfill a very real market need that Git didn't/doesn't handle large files very well.

I believe it is inevitable that Git will gain better support for handling of large files, as this seems like a critical feature for a popular version control tool.

If you make this long bet, LFS is only an interim solution and its value proposition disappears after Git has better native support for large files.

LFS as a stop gap solution would be tolerable except for the fact that...

Git LFS is a One Way Door

The adoption or removal of Git LFS in a repository is an irreversible decision that requires rewriting history and losing your original commit SHAs.

In some contexts, rewriting history is tolerable. In many others, it is an extremely expensive proposition. My experience maintaining version control in professional contexts aligns with the opinion that rewriting history is expensive and should only be considered a measure of last resort. Maybe if tools made it easier to rewrite history without the negative consequences (e.g. GitHub would redirect references to old SHA1 in URLs and API calls) I would change my opinion here. Until that day, the drawbacks of losing history are just too high to stomach for many.

The reason adoption or removal of LFS is irreversible is due to the way Git LFS works. What LFS does is change the blob content that a Git commit/tree references. Instead of the content itself, it stores a pointer to the content. At checkout and commit time, LFS blobs/records are treated specially via a mechanism in Git that allows content to be rewritten as it moves between Git's core storage and its materialized representation. (The same filtering mechanism is responsible for normalizing line endings in text files. Although that feature is built into the core Git product and doesn't work exactly the same way. But the principles are the same.)

Since the LFS pointer is part of the Merkle tree that a Git commit derives from, you can't add or remove LFS from a repo without rewriting existing Git commit SHAs.

I want to explicitly call out that even if a rewrite is acceptable in the short term, things may change in the future. If you adopt LFS today, you are committing to a) running an LFS server forever b) incurring a history rewrite in the future in order to remove LFS from your repo, or c) ceasing to provide an LFS server and locking out people from using older Git commits. I don't think any of these are great options: I would prefer if there were a way to offboard from LFS in the future with minimal disruption. This is theoretically possible, but it requires the Git core product to recognize LFS blobs/records natively. There's no guarantee this will happen. So adoption of Git LFS is a one way door that can't be easily reversed.

LFS is More Complexity

LFS is more complex for Git end users.

Git users have to install, configure, and sometimes know about the existence of Git LFS. Version control should just work. Large file handling should just work. End-users shouldn't have to care that large files are handled slightly differently from small files.

The usability of Git LFS is generally pretty good. However, there's an upper limit on that usability as long as LFS exists outside the core Git product. And LFS will likely never be integrated into the core Git product because the Git maintainers know that LFS is only a stop gap solution. They would rather solve large files storage correctly than ~forever carry the legacy baggage of having to support LFS in the core product.

LFS is more complexity for Git server operators as well. Instead of a self-contained Git repository and server to support, you now have to support a likely separate HTTP server to facilitate LFS access. This isn't the hardest thing in the world, especially since we're talking about key-value blob storage, which is arguably a solved problem. But it's another piece of infrastructure to support and secure and it increases the surface area of complexity instead of minimizing it. As a server operator, I would much prefer if the large file storage were integrated into the core Git product and I simply needed to provide some settings for it to just work.

Mercurial Does LFS Slightly Better

Since I'm a maintainer of the Mercurial version control tool, I thought I'd throw out how Mercurial handles large file storage better than Git. Mercurial's large file handling isn't great, but I believe it is strictly better with regards to the trade-offs of adopting large file storage.

In Mercurial, use of LFS is a dynamic feature that server/repo operators can choose to enable or disable whenever they want. When the Mercurial server sends file content to a client, presence of external/LFS storage is a flag set on that file revision. Essentially, the flag says the data you are receiving is an LFS record, not the file content itself and the client knows how to resolve that record into content.

Conceptually, this is little different from Git LFS records in terms of content resolution. However, the big difference is this flag is part of the repository interchange data, not the core repository data as it is with Git. Since this flag isn't part of the Merkle tree used to derive the commit SHA, adding, removing, or altering the content of the LFS records doesn't require rewriting commit SHAs. The tracked content SHA - the data now stored in LFS - is still tracked as part of the Merkle tree, so the integrity of the commit / repository can still be verified.

In Mercurial, the choice of whether to use LFS and what to use LFS for is made by the server operator and settings can change over time. For example, you could start with no use of LFS and then one day decide to use LFS for all file revisions larger than 10 MB. Then a year later you lower that to all revisions larger than 1 MB. Then a year after that Mercurial gains better native support for large files and you decide to stop using LFS altogether.

Also in Mercurial, it is possible for clients to push a large file inline as part of the push operation. When the server sees that large file, it can be like this is a large file: I'm going to add it to the blob store and advertise it as LFS. Because the large file record isn't part of the Merkle tree, you can have nice things like this.

I suspect it is only a matter of time before Git's wire protocol learns the ability to dynamically advertise remote servers for content retrieval and this feature will be leveraged for better large file handling. Until that day, I suppose we're stuck with having to rewrite history with LFS and/or funnel large blobs through Git natively, with all the pain that entails.


This post summarized reasons to avoid Git LFS. Are there justifiable scenarios for using LFS? Absolutely! If you insist on using Git and insist on tracking many large files in version control, you should definitely consider LFS. (Although, if you are a heavy user of large files in version control, I would consider Plastic SCM instead, as they seem to have the most mature solution for large files handling.)

The main point of this post is to highlight some drawbacks with using Git LFS because Git LFS is most definitely not a magic bullet. If you can stomach the short and long term effects of Git LFS adoption, by all means, use Git LFS. But please make an informed decision either way.