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I have a number of standard projects set up for QGIS users. Some of them take more than 5 minutes to load. Things recently got much worse suddenly - and I want to track down why.

Are there any methods to check what stages of loading a project are slowing things down or/and how long QGIS is taking over each stage of loading a project?

In my particular case the issue may be related to internal network overload, and seems to be related to upgrades (at the same time) from Windows 7 to Windows 10 and QGIS 2.18 to QGIS 3.4. However, I think answers will be more useful for others/Stackexchange if they consider the wider question.

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  • I noticed that QGIS 3 is slower than QGIS 2 to open. And the number of pre defined Layouts in the Project, as their size, cause a delay too. Not sure if Models in the Project cause it too. Try checking this. Commented Jun 14, 2019 at 18:50
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    Deleting the one print layout has made no difference - and no there are no models - but thanks for the suggestion/ Commented Jun 18, 2019 at 13:51
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    Slow loading may have different reasons (with 3.x print layouts seem to be not anymore one of them). Usually unavailable WMS/WFS add the most delay - you can test this by starting similar projects, one with and one without webservices. Also, with very large project files the loading can take a lot of time. I try to limit my .qgs file sizes to 10 MB to avoid this. If the issue persists you could add some more details on your project files and your data structure?
    – Erik
    Commented Apr 16, 2020 at 8:57
  • If it is QGIS that is slow to load, you can check plugin load times using: plugins.qgis.org/plugins/PluginLoadTimes Commented Apr 21, 2020 at 15:32
  • gis.stackexchange.com/questions/367591/… fixed my issue.
    – Cary H
    Commented Jun 10, 2021 at 19:07

6 Answers 6

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I had issues with slow loading of QGIS in a general sense. What helped me was the unchecking my installed plugins so that they don't load on startup. This helped independent of what version I was using.

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    But the question is about "slow loading of QGIS project" not "slow loading of QGIS". :) Removing plugins decreases just loading of QGIS. Generally, this doesn't decrease loading a project.
    – menes
    Commented Jun 6, 2020 at 16:11
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One idea is to load it without rendering and check the load time. Then turn rendering on and try different layers one by one.

Also check for feature counting on layers as that can slows thing down.

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Deleting complex print layouts really helped to reduce the loading time of my QGIS projects.

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Did you try out the Debugging/Development Tools? They are availably since QGIS 3.16.

The tool analyses the time it takes to load each layer from a QGIS project.

Go to View --> Panels --> Debugging/Development Tools and click on the Profiler in the left menu.

Select Project Load from the category list.

Expand the entry called "Reading map layers" in the profiler tree. Now you can see the loading time of each layer.

enter image description here

It is also described in this post: Measuring loading time of each layer when opening a QGIS project

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  • I ran the Debugging tools and the problem I had with a slow loading Project file was obvious. Over a 100 saved map layouts from another job. Using Layout Manager I deleted them...loads in seconds not minutes.
    – Dan R
    Commented Apr 6, 2023 at 15:07
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In my case I opened a fairly large QGIS 2.6 project in QGIS 3.16 and it took an extremely long time to load, almost an hour. In 2.6 the same project file takes a minute or so to load on the same Windows 7 machine.

I isolated the problem to an 81000 row CSV layer. The CSV file used newlines for the row delimiters, and QGIS 3 apparently needs cr-lf delimiters (at least on Windows). This caused it to treat the entire file as a single massive row.

After I saved the CSV file from Wordpad (which converted the delimiters to cr-lf), the load time in QGIS 3 was normal.

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Based on this never being answered, I now assume that there must be no way to do what I asked about - which is to find out by some standard method what is taking the time.

Other answers provide a selection of ideas for tracking down some of the potential issues.

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