5000

In SharePoint 2013 online, we are facing the threshold value and unable to increase the threshold value because of cloud server control. More than 5000 data/item in list can't retrieve from database in single call which affects the list item to view.To resolve this,we can go for the indexing and filtered view. it will help to see all item if it exceed more than 5000 items in the list. 5000 item is set as default in SharePoint online list to maintain the performance.

If yoy'll talk about items threshlod limit so it was 5000 as site collection level and 10000 as farm level.But default value is 2000.You can extend from central administrator.

Thresholds are those that have a default value that cannot be exceeded unless the value is modified. Thresholds can, in certain circumstances, be exceeded to accommodate variances in your farm design, but it is important to understand that doing this may affect the performance of the farm in addition to the effective value of other limits. The default value of certain thresholds can only be exceeded up to an absolute maximum value. A good example is the document size limit. By default, the default document size threshold is set to 250MB, but can be changed to support the maximum boundary of 2GB.