This topic describes the case sensitivity for parts of the OneDrive REST API in detail.
The URL scheme and authority (DNS name) are treated as case-insensitive. The URL path may have case-sensitive or case-insensitive components, depending on the type of resource being addressed. Be sure to consider everything documented here.
Resource identifiers like drive-id, item-id are case-sensitive.
File system path identifiers used with colons (such as :/Documents/MyFile.xlsx) and
filenames specified in the URL (such as 'MyFile.xlsx' in /items/{item-id}/children/MyFile.xlsx)
are not case-sensitive.
For example, the path :/Folder-A/Foo.txt is treated the same as :/folder-a/foo.TXT.
Likewise, the path /items/{item-id}/children/Foo.txt is treated the same as /items/{item-id}/children/FOO.TxT.
Metadata path identifiers, such as '/items/{item-id}/image' are case-sensitive.
The request query parameter names are case-sensitive. For example, ?select is not
the same as ?SELECT.
Per HTTP 1.1 protocol, request header names are not case-sensitive.
For example, Content-Type would be treated the same as content-type.
The request header values are case-sensitive. For example, when providing an
eTag or cTag value in an if-match header, the tag is case-sensitive.
The keys of the JSON object suppled in the request body are case-sensitive. The value supplied in name-value pairs is stored as-is into the service.
In the JSON response, the property names are camel-cased. The value of the property (such as item name) is returned as stored in OneDrive.