CSS & Javascript truncated by nginx 16

On several recent projects I’ve been using VirtualBox and Vagrant to spin up new development machines. The simplicity and power of the two tools together is amazing, and stops me from cluttering up my main machine with tools and packages from random side projects. It hasn’t been all sweetness and light though. I wrote recently about issues with node.js, npm and express, and this week ran in to a far more frustrating issue. It involved nginx and sendfile, with javascript truncated and this developer frustrated.

The Problem: CSS & Javascript truncated

My setup was a very basic one – a VirtualBox running:

  • Ubuntu 12.04
  • nginx

My code was mounted from a windows host, and initially all was going well. Then suddenly my app started spitting out javascript errors. Digging in to chrome’s error console, it looked like the last 40 or 50 bytes of the file were missing. As these bytes contained the end of a function, them being absent meant the file had invalid syntax so the application didn’t run. It was a similar story with the css – random bits chopped off the end of some files, and in others changes I made not being reflected when viewed in the browser. Javascript truncated, the same for css – bad times all round.

Javascript truncated? Bad times

I suspected a cache issue initially. I flushed the browser cache, tried a new browser, and even restarted nginx on the vm – all to no avail. Interestingly, when I added more code to the bottom of an affected javascript file, it was still only the last 40-50 bytes being chopped off – the file itself wasn’t frozen in it’s original, broken state. So, what’s going on there?


Nginx has a sendfile directive, which defaults to on. It allows nginx to use the Linux kernel’s sendfile() operation to read the requested file from disk. This is typically quicker than using read() and write(). So far, so good.

The problem is that sendfile doesn’t work so well in virtual environments, as noted in nginx’s “Pitfalls” section. The fix turned out to be insanely simple – just turn sendfile off. As it’s a development machine, the performance hit incurred by turning off this feature is pretty negligible. (It would want to be a pretty significant performance hit to outweigh the file truncation!)
In the nginx config http server block, I added:

sendfile off;

Once nginx was restarted, I was getting served full static files, and all was well with the world again!

16 thoughts on “CSS & Javascript truncated by nginx

  1. Reply Matthew Setter Jan 17,2014 7:58 pm

    Thanks kindly for your post, it’s just made my day. I’ve had exactly the same issue and have been scratching my head wondering how to phrase a Google search, let alone find the answer. Wicked stuff.

  2. Reply Jonathan Hanson Mar 2,2014 5:36 am

    Holy ever living crap. I just lost 2 hours of my life to this issue, and would’ve kept on losing had I not found this article.

    I rarely comment on blogs, but man I just had to say thanks.

  3. Reply Ethan Wayne Apr 17,2014 10:41 pm

    Thank you for this post. Saved me a bunch of time. Thanks again!

  4. Reply Meet Matt Jul 29,2014 2:58 pm

    Thank you so much!!! I have wasted so much time during development because of this bug!!!!!

  5. Reply Greg Sep 20,2014 5:14 am

    I wanna kill something. Not you, my friend – you are a sanity saviour. A beer. I need to kill several beers.

  6. Reply Andre B. Sep 25,2014 10:53 pm

    Woot! Awsome! Thanks for posting this! This is exactly the issue I was having.

  7. Reply Ismael Nov 14,2014 1:14 pm

    You just save my life!! Great!

  8. Reply Juan Diego Nov 27,2014 5:18 pm

    excellent! i’m using it in every new project

  9. Reply Tine Klancar Jan 31,2015 11:19 pm

    You just saved a very bad day of mine. Where can I buy you some coffee??

  10. Reply Vincent Feb 6,2015 1:20 pm

    Thanks! That was a big WTF for me.

  11. Reply Jean Oct 19,2015 7:33 pm

    Thanks! You just saved my… evening.

  12. Reply izolate Nov 4,2016 12:21 pm

    Many thanks for saving me from frustration

  13. Reply Richard Dec 2,2016 8:08 am

    Wow! Amazing!

  14. Reply david Mar 9,2017 2:20 pm

    Thanks so much!

  15. Reply Joe Jun 25,2017 7:23 pm

    This was a total WTF moment watching files get truncated or null terminating bytes get added.

    Thanks for the quick fix!

  16. Reply Matt Fletcher Aug 1,2018 4:29 pm

    I wish I could reiterate what the others here are saying, but unfortunately this didn’t fix my problem 🙁

    I’ll report back if I discover what it is- I’m not using a virtual container, just Perusio’s drupal nginx config on a Mac.

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