Improving Flash Builder’s performance

For those of you who are having performance issues with Flash Builder, it could be that the Java heap-size settings are too low. Here is a quick and easy fix, which should make Flash Builder easier to use. People on Twitter who have tried this modification report better leverage of their hardware and overall improved performance.

For Windows:

  1. Navigate to your FlashBuilder folder – C:\Program Files (x86)\Adobe\Adobe Flash Builder 4.5\
  2. In a text editor, open FlashBuilder.ini (for Windows) and Adobe Flash Builder 4.5.ini within Contents/MacOS/folder (for Mac OSX) .
  3. Find the lines that says “Xms40m” and “Xmx512m” (Please note: the numbers may already be configured).
  4. Replace these two lines with “Xms256m” and “Xmx512m” respectively.
  5.  Save the file and restart FlashBuilder.

For Mac OSX:

  1. Open a Terminal window
  2. Navigate to Applications/Adobe Flash Builder 4.5/Adobe Flash Builder (you may need to enclose these folder names in quotes).
  3. In a text editor, such as vi or emacs, open Adobe Flash Builder 4.5.ini.
  4. Find the lines that says “Xms40m” and “Xmx512m” (Please note: the numbers may already be configured).
  5. Replace these two lines with “Xms256m” and “Xmx512m” respectively.
  6.  Save the file and restart FlashBuilder.


Hope that helps,


Courtesy of: polygeek and dougrdotnet



4 Responses to Improving Flash Builder’s performance

  1. n!co says:

    I already up to -Xms768m -Xmx1024m and Flash Builder builds ever and ever and ever !

    Please, give us a flex compiler with a real and performant incremental build.

    A java developer which shift on flex half time

  2. Rick Winscot says:

    Tweaking the JVM settings via the .ini significantly improves Flash Builder speed, response, and compile times. If you haven’t tried it yet – I would definitely recommend you close Eclipse right now and make the changes. You’ll be glad you did.

    The sad news is that the performance issues that I’ve been seeing recently (after an upgrade to Flash Builder 4.5) aren’t solved by making more system resources available to the IDE. It’s bad… I’m seeing _frequent_ RTEs that lock / hang the IDE with log messages like “Marker id not found”, “Failed to execute runnable (java.util.ConcurrentModificationException)”, “Failed to execute runnable (java.lang.NullPointerException)”, and “Unhandled event loop exception”.

    It looks like I’m not the only one…

    IMO, the real productivity killers and performance problems aren’t getting sufficient attention; fixes aren’t getting pushed out often enough. Is it not possible to update Flash Builder more often? Waiting six or more months at a time for fixes… in Internet time, is like… forever.

  3. Pingback: Flash builder performances | Maug – Moroccan Adobe User Group

  4. There are actually more ways you can improve FlashBuilder / Eclipse speed.

    1. Disable unecessary validations and startup action in eclipse reference.
    2. Modify eclipse.ini to set the Xmn(new generation size), Xms and Xmx, enable parallel GC
    3. Create a ram disk(virtual disk) on memory, and put your jdk on the ram disk.
    4.Make sure you are using sun jdk, not open jdk/gcj nor other jdk on linux
    5.Disable antivirus software, or add your jdk & eclipse & workspace & other related folder to white list in your antivirus software.

    The complete post and description for each step can be found here