Optimize your thumbnail text for maximum click-through rate based on style and emotion.
3-6 words maximum. The thumbnail text should complement your title — not repeat it. Together, title + thumbnail should create more curiosity than either alone.
Never — that's wasted space. Your title already shows below the thumbnail. Use thumbnail text to add a different dimension: add a number, a reaction word, or a short power phrase that makes the title more compelling.
Bold, heavy-weight sans-serif fonts (Impact, Bebas Neue, Anton) are industry standards. They're readable at tiny sizes and create visual impact. Avoid thin fonts, cursive, and decorative fonts.