How frequently does IMPORTRANGE refresh?

How frequently does the importrange function refresh and reload the source data?

How often does Importrange update?

By default, the IMPORTRANGE function recalculates every 30 minutes (source).

Is there a limit for Importrange?

ImportRange formulas: 50 cross-workbook reference formulas. ImportData, ImportHtml, ImportFeed, or ImportXml formulas: 50 functions for external data. Maximum string length is 50,000 characters.

How often does Google Sheets import data?

Sheets will update the data automatically at up to 1 hour intervals , using the IMPORTDATA() function, which is very similar to IMPORTRANGE().

When closed

Never.Spreadsheets update external api only onOpen(). But there is no documentation and this may change in the future.

When open, 30 minutes

Functions that pull data from outside the spreadsheet recalculate at the following times:
ImportRange: 30 minutes
ImportHtml, ImportFeed, ImportData, ImportXml: 1 hour
GoogleFinance: may be delayed up to 20 minutes

Opening the spreadsheet refreshes all the functions.