The Text Structure Visualizer turns a document into an abstract picture of itself. Every letter, digit and symbol is swapped for a block or a mark of your choice, while the spaces, tabs and line breaks stay exactly where they were. What is left is the skeleton of your page: how long each line runs, where the paragraphs and indented blocks sit, how heavy the text is, and how the whole thing is balanced. Designers call this old trick greeking - it is the same idea as the grey placeholder text in a website mock-up, except here you keep the true shape of your own writing instead of borrowing somebody else's filler.
The tool draws one glyph for every visible character, so the picture is a 1:1 copy of your text's geometry - columns never shift, and a line that was 62 characters long stays 62 glyphs wide. On top of that you can keep punctuation marks and the digits 0–9 in place so full stops and figures still read, expand tabs into real spaces, and wrap long lines to a fixed column width. A statistics panel reports lines, characters, words, blank lines, the longest and average line length, the number of glyphs drawn and the overall ink density, and the finished picture can be copied or downloaded as a text file.
So why is that useful? Because the words are usually the last thing you should worry about when you judge layout. Shading a page like this makes an over-long paragraph, a top-heavy section, a ragged column or an unbalanced two-page spread obvious at a glance - before you have chosen a font size, a column width or a final word count. The same picture answers questions such as "is this section too dense?", "do these two columns look similar in length?" or "how much white space does this page really have?", without reading a single sentence. It is also a quick way to give a mock-up a believable texture, and to produce redaction-style visuals or plain-text art.
It is written with plain vanilla JavaScript - no libraries and no frameworks - and runs entirely inside your browser. Your text is processed on your own device, never uploaded anywhere, and the page keeps working while you are offline once it has loaded. The only thing that leaves the tool is whatever you choose to copy or download.