[null,null,["上次更新時間：2025-08-29 (世界標準時間)。"],[],[],null,["# Synchronizing Clients with Gmail\n\nKeeping your client synchronized with Gmail is important for most application\nscenarios. There are two overall synchronization scenarios: full synchronization\nand partial synchronization. Full synchronization is required the first time\nyour client connects to Gmail and in some other rare scenarios. If your client\nhas recently synchronized, partial synchronization is a lighter-weight\nalternative to a full sync. You can also use [push notifications](/workspace/gmail/api/guides/push)\nto trigger partial synchronization in real-time and only when necessary, thereby\navoiding needless polling.\n\nContents\n--------\n\nFull synchronization\n--------------------\n\nThe first time your application connects to Gmail, or if partial synchronization\nis not available, you must perform a full sync. In a full sync operation, your\napplication should retrieve and store as many of the most recent messages or\nthreads as are necessary for your purpose. For example, if your application\ndisplays a list of recent messages, you may wish to retrieve and cache enough\nmessages to allow for a responsive interface if the user scrolls beyond the\nfirst several messages displayed. The general procedure for performing a full\nsync operation is as follows:\n\n1. Call [`messages.list`](/workspace/gmail/api/v1/reference/users/messages/list) to retrieve the first page of message IDs.\n2. Create a [batch request](/workspace/gmail/api/guides/batch) of [`messages.get`](/workspace/gmail/api/v1/reference/users/messages/get) requests for each of the messages returned by the list request. If your application displays message contents, you should use `format=FULL` or `format=RAW` the first time your application retrieves a message and cache the results to avoid additional retrieval operations. If you are retrieving a previously cached message, you should use `format=MINIMAL` to reduce the size of the response as only the `labelIds` may change.\n3. Merge the updates into your cached results. Your application should store the `historyId` of the most recent message (the first message in the `list` response) for future partial synchronization.\n\n| **Note:** You can also perform synchronization using the equivalent [`Threads` resource](/workspace/gmail/api/v1/reference/users/threads) methods. This may be advantageous if your application primarily works with threads or only requires message metadata.\n\nPartial synchronization\n-----------------------\n\nIf your application has synchronized recently, you can perform a partial\nsync using the [`history.list`](/workspace/gmail/api/v1/reference/users/history/list)\nmethod to return all history records newer than the `startHistoryId` you specify\nin your request. History records provide message IDs and type of change for\neach message, such as message added, deleted, or labels modified since the time\nof the `startHistoryId`. You can obtain and store the `historyId` of the most\nrecent message from a full or partial sync to provide as a `startHistoryId` for\nfuture partial synchronization operations.\n\nLimitations\n-----------\n\nHistory records are typically available for at least one week and often\nlonger. However, the time period for which records are available may be\nsignificantly less and records may sometimes be unavailable in rare cases. If\nthe `startHistoryId` supplied by your client is outside the available range of\nhistory records, the API returns an `HTTP 404` error response. In this case,\nyour client must perform a full sync as described in the previous section."]]
