Serious Lag and Memory Buildup in Long Storyline360 Course – Suspected Media Unloading Issue

Hello Sagar_Mavale​, 

I'm sorry to hear that you're running into similar behavior. I understand that you are experiencing a significant lag with your Storyline project. 

• Are you working and saving your project locally? We recommend working from your local hard drive to avoid erratic behavior.
• As my colleague EricSantos​ recommended earlier in this discussion, the steps in this article can help fix the erratic behavior. Do you notice any improvement if you follow these steps? 

When working with larger files, it's generally a good idea to break them up into smaller chunks. You might also find some inspiration in this discussion post. 

If you're still experiencing this behavior, we'd be happy to take a closer look at your project file (.story) in this thread or privately in a support case so we can investigate this further. 

Looking forward to hearing from you!

Hi John, thanks for the response.
this file does not have any video in it.

Why “lag” means different things in Storyline

There are a number of discussions here in which people say their course is “lagging,” but they are often talking about very different things. It helps to separate them into three categories:

1. Slow screen loads / navigation delays
   • Example: clicking Next takes several seconds before the slide appears.
   • Usually related to file size, media preloading, or memory bloat.
2. Timeline desynchronization
   • Example: the narration plays fine, but Storyline’s timeline (seek bar, animations, triggers) starts running behind.
   • Audio and visuals drift apart over time.
3. Video/audio sync drift
   • Example: lips don’t match speech in a video.
   • Typically an encoding or streaming issue.

Which one applies here?
From what you describe — “the audio finishes playing, but the seek bar lags significantly, especially after 30 minutes” — this is timeline desynchronization (2).

It’s not about slide loading or video playback. It’s specifically the Storyline timeline struggling to keep up during long runtimes.

Why this happens:

OrvinCastanha​ 's original hypthesis is on the right track: Storyline does not aggressively unload assets once they’re in memory. Instead, it tends to cache everything the learner has already visited. That leads to:

• Memory bloat from accumulated images/audio.
• Laggy transitions and slower interactions as the session goes on.
• Worse drift when slides have many layers, long audio clips, or embedded video.
• Extra strain if you try to preload media (you’re right to stop doing this).

Unfortunately, there’s no way within Storyline to force a “memory clear” between slides or scenes. Once a course is running in the browser, only a tab refresh resets memory.

What you can do

• Break the course into smaller modules. 80 slides / 150 MB in a single SCORM is on the heavy side; splitting into 20–30 minute topics dramatically reduces drift.
• Chunk audio and sync to audio completion. Instead of one long timeline, use shorter narration files and trigger layers/animations off “media completes.” This masks drift because each chunk realigns timing.
• Reduce slide complexity. Avoid very long timelines with multiple layered interactions. Fewer layers = fewer objects left in memory.
• Test across browsers. Chrome is often worst at memory management; Edge or Firefox may perform better.
• Avoid unnecessary preloading. It frontloads memory use and accelerates bloat.

Bottom line
What you’re running into is a known limitation: Storyline’s browser-based player holds onto assets rather than releasing them. The visible symptom is timeline drift after 20–30 minutes.

I'm not aware of a silver-bullet fix, but design strategies (smaller modules, shorter audio chunks, simpler slides) can mitigate it and keep performance at a level stakeholders can accept.