Should I test button text, color, size, or placement?

You've got a button to test and four things you could change: the text, the color, the size, and where it sits in the email. The temptation is to test all of them at once. Don't. Change two things at the same time and you'll never know which one moved the needle.

Here's a practical order to work through, based on what tends to drive the most difference:

Start with button text. This is usually where the biggest gains live. "Start Free Trial" versus "Get Started" versus "Try It Now" can produce meaningfully different click rates because the words carry different weight. One feels like a commitment. Another feels like a low-stakes nudge. Test one variable, wait for enough clicks to be meaningful, then lock in a winner before touching anything else.

Then test placement. Above the fold versus below it. Right after the main message versus tucked away at the bottom. Near a product image versus standing alone. Context shapes action, and a well-placed button with good text will outperform a misplaced one with great copy.

Color comes third. High-contrast often beats blending in with your brand palette, but the effect is usually smaller than people expect. Think of color as a supporting player, not the lead. That said, if your button is competing visually with everything else in the email, fixing that contrast is worth testing.

Size is last. Bigger is generally better, especially for mobile readers, but you'll get less bang for your buck here compared to text and placement. Test size if you genuinely suspect it's holding clicks back, not as your opening move.

The overall principle is simple. Text tells people what to do and why. Visual elements help them actually do it. Get the message right first, then fine-tune how it looks.

And if you're running A/B tests on CTAs already, the same logic applies. One variable per test, every time. It takes longer, but you'll end up with results you can actually trust.