Access token (API key) is special string used to authorize user to upload collected measurements to OpenCellID database.

The correct key must consist of digits 0-9 and letters a-f. Depending on registration date key format may look like this:

• pk.9743a66f914cc249efca164485a19c5c – 32 characters, preceded with 'pk.', total 35 characters
• 9743a66f914cc249efca164485a19c5c – 32 characters
• 9743a66f-914c-c249-efca-164485a19c5c – 32 characters in five groups separated by dash, total 36 characters
• 9743a66f914cc2 – 14 characters