Most product categories only allow a total of 249 Bytes accross for all backend keywords.
As soon as there are more than 249 Bytes, all backend keywords would not be indexed anymore.
Special Characters (2x), Hypens, Commas & Spaces all count towards Bytes
Special Characters (eg. ä, ü, ö, ß, &, é) count as 2 bytes and in some cases even more.
Normal characters, Hyphens, Commas & Spaces count as 1 Byte.
Find out more about the limit change in our Blog (click here).
Seller Central Template for Backend Keywords
The "Optimize keywords" feature in Sellics provides the option to summarize all researched keywords into 249 Bytes.
This article and video (click here) explains how to use the Optimize Keywords feature.
Additionally, more space can be saved by using hyphens. This is explained further in this article (click here).