Installing and Running the CalTopo Offline App - macOS

To install the CalTopo Offline App you will need:

  • CalTopo App
  • CalTopo map data for your desired area
  • Java Standard Edition JDK

Installation Instructions

  1. Download and install the CalTopo app

    Decide whether you want to install CalTopo Offline on your computer's hard drive, a thumb drive or an external hard drive. Depending on how much map data you plan to download, it may not fit on your computer's hard drive. If you're not sure, start by installing it to your computer's hard drive now, it can be copied to another drive later if needed.

    Sign-in to your GIS account on

    Click on your account name at the top of the left bar, then the "Offline Access" tab, or go directly to

    Click on "fresh install" and download the file to your computer.


    In Finder, go to the folder that contains the file (probably Downloads) on your computer. Double click "" to open it. The file is unzipped to a "caltopo" folder.


    For security reasons, MacOS requires you to move downloaded applications to a new location before running them. In Finder, open the "mac - read instructions" folder and drag the "CalTopo Offline" app into the "caltopo" folder above it.


    Now delete the "mac - read instructions" folder.


  2. Download the map data.

    CalTopo Offline is installed without any map tiles. To download the map tiles for your desired area, go to

    The red-shaded areas indicate areas where offline maps and data are available. Hover the mouse over a portion of the red-shaded areas and a solid-red, one degree square will appear.


    Click on the solid-red square of the block that you would like to download. On the right side of the page, a list of available data for that one degree square appears.

    Download the data files by clicking on the size of each file. Its important that you download all of the files.


    Drag all of the mbtiles files into the the caltopo > data > tiles folder.


    Repeat the above steps for additional one degree blocks as needed.

    To keep clutter out of your Downloads folder, it's a good practice to drag the "caltopo" folder from the "Downloads" folder to your home folder.


  3. Install Java Standard Edition JDK
    Go to, click on "Java Platform (JDK)".


    To download the installation file, click "Accept License Agreement" and the link for "Mac OS X".


Once the installation file is downloaded, open it to run it. Accept all of the default installation options.

Running CalTopo Offline

CalTopo Offline is essentially the same program as Whereas is hosted by a web server in the Internet cloud, CalTopo Offline is hosted by a local web server on your computer. In both cases you use a web browser to interact with the server.

Therefore it takes two steps to run CalTopo Offline:

  1. Start the CalTopo Offline server:

    In Finder, open the "caltopo" folder and right-click on the "CalTopo-Offline" file and select "Open".


    Your computer will ask if you are sure you want to run an app from an "unidentified developer". Click "Open".


    After the first time, you can run the app by just clicking on it.

    A CalTopo Offline console window will open. You can minimize this window, but don't close it.


    The server is now started and you can go to a browser to access the functionality.

  2. Open a web browser (Chrome is recommended). On a new tab, go to http://localhost:8080.


    The server may take some time to get up and running. If initially you get a web page error (e.g. a “This webpage is not available” or "This site can’t be reached" message), then the local web server may need more time to get fully started. Wait for a few seconds and refresh the page.

Stopping the CalTopo Offline server

When you are finished using CalTopo Offline:

  1. Close the CalTopo Offline tab in your browser
  2. Click "Cancel" and then "Quit" in the CalTopo Offline Console


Accessing the CalTopo Offline server from another computer

If multiple computers are on the same Local Area Network (e.g. connected to the same router), each of the computers can connect to the CalTopo Offline server running on one of the computers. To do so, each computer opens an web browser and enters the Server Address displayed in the CalTopo Offline console (eg. http://My.Mac.local:8080).

Updating CalTopo Offline to a New Version

To update your version of CalTopo Offline, download a new version of the cal.jar file to your caltopo folder.

Click on ??? to


Click on "JAR only" and move the cal.jar file from your Downloads folder to your caltopo folder.