
pixels are the default unit so don't change it to "256px", just plain "256".

Change (or add) the width and height attributes to whatever you want t to be.In this case, for example, my SVG has width and height set to 100%:

Check if it has the width and height attributes. Just take a look at the element the beginning of the code. For example, in Notepad or Notepad++ in Windows. You specify the size of the viewport using the width and height attributes of the element. One of the things you can edit is the ViewPort (think canvas) dimensions of the SVG.

You could then use the text editing functionalities of your favourite text or web editor (such as "replace in all open files") to make bulk changes. This means that you can edit the SVG (carefully) as regular text just like you would edit a web page. This is a "hacky" way of doing it (if you are not a coder), but since you are looking for alternative solutions, here we go.
