Is it possible to use Hugo Pipes to replace some content, for example convert some spaces to non-breakable ones, or have I to keep this kind of tasks in say Gulp (parsing all html files)?
See gulpfile example.
You could use the replace or replaceRE functions in your templates
I saw these functions, but how can I pass the whole page as the INPUT of the function?
You can pass the content using .Content
- and perform multiple replacement at once then return the modified content, just as a markdown parser for example or a gulp task?
Try it out and see 
Yes I’ll try tomorrow, thank you!
This should help me too:
https://discourse.gohugo.io/t/refactor-multiple-replace-statements/9994
Do you have any idea why
{{ replace .Content "A" "B" | safeHTML }}
is working, but
{{ .Content | replace "A" "B" | safeHTML }}
returns
A
?
I think both are working, but work in another way as you expect.
{{ replace .Content "A" "B" }} Replaces every “A” inside .Content with “B”
But {{ .Content | replace "A" "B" }} Replaces every occurrence of “B” it finds in “A” with the value of .Content. And as it does not find any B in “A” it could replace, it leaves it as “A”.
So the following two will do the Same:
{{ replace "ABC" "A" "X" }} outputs XBC
{{ "X" | replace "ABC" "A"}} outputs XBC
Indeed thank you for pointing this out!
However then I can’t pipe multiple replace on .Content…
I think I will keep this kind of replacement in my gulpfile 
You could do it like this
{{ $content := replace .Content "A" "B" }}
{{ $content = replace $content "C" "D" }}
...
{{ $content }}This works, thank you!