# LaTeX/MathJax does not render in some question thumbnail

Sometimes I have question thumbnail that does not render LaTeX:

I have compared my code with other posts, I do not found differences that can explain this behavior.

What can cause LaTeX or MathJax not to render in thumbnails?

• The $\rm\LaTeX$ is not complete in the excerpt generating the thumbnail, and thus does not compile. – Asaf Karagila Dec 4 '18 at 10:05
• Thank you for being reactive. I am sorry I do not understand what you meant? What LaTeX is not complete? I have no LaTeX error within the post itself. – jlandercy Dec 4 '18 at 10:07
• The thumbnail is generated by clipping some part of the question. This clipping does not contain the entire $\rm\LaTeX$ code, and therefore does not compile. – Asaf Karagila Dec 4 '18 at 10:09
• Ok, this makes sense. Thus having a long LaTeX code at the beginning of the post lead to cropped LaTeX and does not render. Thank you it is clear now. I you mind making it an answer I will be glad to accept it. – jlandercy Dec 4 '18 at 10:12

The thumbnail is generated by cropping part of your question. Since the $$\rm\LaTeX$$ is not fully within that cropped part, the code does not compile.
One could argue in favor of changing the code of the excerpt generator to always complete the $$\rm\LaTeX$$ code if the crop happens halfway through it, but this opens up a few different problems. For example people using align environment or other multiline environment that would end up taking far more display real estate than originally intended.