---
title: "Honey, I shrank the JARs - Mostly nerdless"
url: https://daily.dev/posts/honey-i-shrank-the-jars---mostly-nerdless-ndnbulwiu
source_url: https://mostlynerdless.de/blog/2026/04/30/honey-i-shrank-the-jars
type: article
source: "Mostly Nerdless"
published: 2026-04-30T14:18:57.098Z
updated: 2026-04-30T14:19:23.192Z
tags: ["java", "maven"]
reading_time: 5
upvotes: 19
comments: 1
language: en
---

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# Honey, I shrank the JARs - Mostly nerdless

**[Mostly Nerdless](https://daily.dev/sources/mostly-nerdless)** · 5 min read · 19 upvotes · 1 comments

## Summary

Femtojar is a new open-source Maven plugin and CLI tool that reduces Java JAR file sizes by up to 50%. It works by packing all class files into a single compressed blob (instead of storing them individually as ZIP entries), using a custom BundleBootstrap classloader to handle execution, and optionally applying ProGuard for bytecode optimization (dead-code removal, inlining). Zopfli compression is used to further optimize the ZIP container. A real-world example shows jstall shrinking from 0.432MB to 0.2MB with MAX compression. The plugin integrates easily into Maven builds with a few lines of pom.xml configuration and supports Java 17+.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://mostlynerdless.de/blog/2026/04/30/honey-i-shrank-the-jars>

## Community discussion

Top comments from developers on daily.dev.

**@theacademe** · 2 upvotes

> This is a fantastic project and an excellent example of the tool chain optimizations we need more of. In my opinion, there's a whole lot of glitz and glamour and splash going on in the tool space today (AI everything everywhere). It's refreshing to see someone tackle a simple, yet present, problem - JAR bloat.
>
>
> Unrelated shout out to [TornadoVM](https://www.tornadovm.org/) and [Unikraft ](https://unikraft.org/)as well for runtime improvement.

---

Tags: [#java](https://daily.dev/tags/java), [#maven](https://daily.dev/tags/maven)

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