Why you should be careful with /groups/{id}/photo and /users/{id}/photo endpoints in MS Graph or unintentional getting photos of big sizes in Graph

As you probably know we may retrieve groups and users photos via Graph API using the following endpoints (see Get photo):

GET /users/{id | userPrincipalName}/photo/$value
GET /groups/{id}/photo/$value

Note however that Graph stores photos of different sizes:

The supported sizes of HD photos on Office 365 are as follows: 48x48, 64x64, 96x96, 120x120, 240x240, 360x360, 432x432, 504x504, and 648x648.

and if we use default /photo endpoint it will return biggest available photo, i.e. 648x648. Depending on your scenario it may not be what you actually need as if you just need to display group logo or group member photo smaller images e.g. of 64x64 pixels size will be enough. And if you work with big photos of 648x648 size and reduce its size by css – page size may be very big and browser memory consumption will be much bigger:

So instead of using default /photo endpoint in MS Graph you may consider using of endpoints which return photo of specified smaller size:

GET /groups/{id}/photos/64x64//$value

or with Graph client library in .Net app:

var stream = Task.Run(async () =>
{
 var photo = await graphClient.Groups[groupId].Photos[Constants.GRAPH_IMAGES_CACHE_PHOTO_ID].Content.Request().GetAsync();
 return photo;
}).GetAwaiter().GetResult();

This code will return small image which may be more appropriate for your scenario:

Compare also sizes for big 648x648 image and small 64x64 image: 10Kb vs 2Kb.