diff --git a/docs/howto/determining-packages.md b/docs/howto/determining-packages.md
new file mode 100644
index 00000000..6e3479a3
--- /dev/null
+++ b/docs/howto/determining-packages.md
@@ -0,0 +1,180 @@
+# Determining Packages in Pangeo Docker Images
+
+For deployments of Pangeo Docker Images using JupyterHub or Binder it can be sometimes unclear to the user exactly which image and tag is being used. Here are the images available as Pangeo Docker Images:
+
+| Image           | Description                                   | 
+|-----------------|-----------------------------------------------|
+| [base-notebook](https://github.com/pangeo-data/pangeo-docker-images/blob/master/base-notebook/packages.txt) | minimally functional image for pangeo hubs | 
+| [pangeo-notebook](https://github.com/pangeo-data/pangeo-docker-images/blob/master/pangeo-notebook/packages.txt) | base-notebook + core earth science analysis packages |
+| [pytorch-notebook](https://github.com/pangeo-data/pangeo-docker-images/blob/master/pytorch-notebook/packages.txt) | pangeo-notebook + GPU-enabled pytorch |
+| [ml-notebook](https://github.com/pangeo-data/pangeo-docker-images/blob/master/ml-notebook/packages.txt) | pangeo-notebook + GPU-enabled tensorflow2 | 
+| [forge](https://github.com/pangeo-data/pangeo-docker-images/blob/master/forge/packages.txt) | pangeo-notebook + [Apache Beam](https://beam.apache.org/) support| 
+
+*Click on the image name in the table above for a current list of installed packages and versions for the most recent tag of each image*
+
+## How to find my current image tag
+
+The environment variable `JUPYTER_IMAGE_SPEC` will tell you what Pangeo Docker Image is currently in use.
+
+In a terminal the command
+
+```
+echo $JUPYTER_IMAGE_SPEC
+```
+
+will work. Within a Jupyter notebook, use
+
+```
+!echo $JUPYTER_IMAGE_SPEC
+```
+
+The image tag may be one of the forms:
+
+- `docker.io/pangeo-data/pangeo-notebook:tag`
+- `pangeo-data/pangeo-notebook:tag`
+- `quay.io/pangeo-data/pangeo-notebook:tag`
+
+The first part is the registry (`docker.io`, which is often omitted, to mean DockerHub or `quay.io`).
+
+The next part the repository of the image itself (e.g. `pangeo-data/pangeo-notebook`)
+
+The tag is the last part. Each image is also assigned a tag of the form `YYYY.MM.DD` indicating when it was last updated.
+
+
+## How to find the list of available image tags:
+
+Using GitHub [Pangeo Docker Images repo](https://github.com/pangeo-data/pangeo-docker-images), the list of select a particular tag from the branches/tag drop down menu. You can also get there directly using https://github.com/pangeo-data/pangeo-docker-images/tags .
+
+## How to finding list of packages in any given tag
+
+Each image has an `packages.txt` file that lists exactly which packages and versions installed in the image.
+
+### Using GitHub UI
+
+On GitHub's website, you can look up any image tag using https://github.com/pangeo-data/pangeo-docker-images/tags . Navigate to the image tag of intereste and select the `packages.txt` file.
+
+### Using the command line with Bash
+
+```bash
+tmp_array=($(echo $JUPYTER_IMAGE_SPEC | tr "/:" "\n"))
+image_name=${tmp_array[1]}
+image_tag=${tmp_array[2]}
+
+packages_url=https://raw.githubusercontent.com/pangeo-data/pangeo-docker-images/$image_tag/$image_name/packages.txt
+
+curl -s $packages_url
+```
+
+### Using a Jupyter notebook with Python
+
+```python
+import os
+image_spec = os.environ['JUPYTER_IMAGE_SPEC']
+_, image_name, image_tag = image_spec.replace('/',':').split(':')
+
+def get_package_list(image_name, image_tag):
+    """Return a list of packages with versions in an image"""
+    packages_url = f"https://raw.githubusercontent.com/pangeo-data/pangeo-docker-images/{image_tag}/{image_name}/packages.txt"
+    
+    import requests
+    packages_str = requests.get(packages_url).content.decode('utf8')
+    
+    packages = []
+    for package in packages_str.splitlines():
+        if package[0] == '#': continue # skip the header
+        package_name, package_version = package.split('==')
+        packages.append((package_name, package_version))
+
+    return packages
+
+packages = get_package_list(image_name, image_tag)
+print(f"{len(packages)} packages found in {image_spec}\n")
+for package in packages:
+    print(f"{package[0]}=={package[1]}")
+```
+
+## How to find difference in packages lists between any two tags
+
+Suppose you want to find out what the differences are between 
+
+`pangeo/pangeo-notebook:2023.06.07`
+
+and
+
+`pangeo/pangeo-notebook:2023.06.20`
+
+to determine which packages were changed, added, or removed?
+
+### Using the GitHub UI
+
+You can compare tags within the GitHub UI by:
+
+1. Finding the release for the tag, from https://github.com/pangeo-data/pangeo-docker-images/tags
+2. Select the tag, so you get something like https://github.com/pangeo-data/pangeo-docker-images/tags
+3. Use the 'compare' dropdown on the left to select another tag to compare it against
+4. Look at the `packages.txt` of the appropriate image.
+
+The link https://docs.github.com/en/pull-requests/committing-changes-to-your-project/viewing-and-comparing-commits/comparing-commits#comparing-tags has additional info.
+
+### Using the command line with Bash
+
+```bash
+image_name=pangeo-notebook
+image_tag_A=2023.06.07
+image_tag_B=2023.06.20
+
+url_A=https://raw.githubusercontent.com/pangeo-data/pangeo-docker-images/$image_tag_A/$image_name/packages.txt
+url_B=https://raw.githubusercontent.com/pangeo-data/pangeo-docker-images/$image_tag_B/$image_name/packages.txt
+
+diff -y --suppress-common-lines  --color <(curl -s $url_A) <(curl -s $url_B)
+
+```
+
+### Using a Jupyter notebook with Python
+
+Using the `get_package_list` function defined above get a list of packages from both tags
+
+```python
+image_name = 'pangeo-notebook'
+image_tag_A = '2023.06.07'
+image_tag_B = '2023.06.20'
+
+packages_A = get_package_list(image_name, image_tag_A)
+packages_B = get_package_list(image_name, image_tag_B)
+```
+
+Determine which packages have been added or removed.
+
+```python
+import difflib
+d = difflib.Differ()
+
+added_packages = dict()
+removed_packages = dict()
+for package in d.compare(packages_A, packages_B):
+    p = package[3:-1].split(', ')
+    name = p[0][1:-1]
+    version = p[1][1:-1]
+    if package[0] == '+':
+        added_packages[name] = version
+    elif package[0] == '-':
+        removed_packages[name] = version
+```
+
+Summarizing
+
+```python
+print(f'Differences in `packages.txt` for {image_name} between {image_tag_A} and {image_tag_B}')
+
+print(f'Packages added:')
+for name in sorted(set(added_packages) - set(removed_packages)):
+    print(f"  {name} {added_packages[name]}")
+
+print(f'Packages removed:')
+for name in sorted(set(removed_packages) - set(added_packages)):
+    print(f"  {name} {removed_packages[name]}")
+
+print(f'Packages changed:')
+for name in sorted((set(added_packages).intersection(set(removed_packages)))):
+    print(f"  {name} {removed_packages[name]} -> {added_packages[name]}")
+```
diff --git a/docs/index.md b/docs/index.md
index df840615..f115e165 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -13,6 +13,7 @@ Curated sets of docker images for doing earth data analysis!
 howto/launch.md
 howto/custom-image.md
 howto/conda-env.md
+howto/determining-packages.md
 contributing.md
 ```