The same tool produces a result you cannot spot and a result you can spot instantly. The difference is almost always in three decisions you make before pressing the button.
1. Box the whole line, not the words you can see
A selection that stops at the baseline leaves the descenders — the tails on g, y, p, q — outside the box. They are copied from the original file, so they survive next to your new text and clash with it.
Box generously: a little above the cap height and a little below the baseline costs nothing, because everything outside the rectangle is untouched either way.
2. Plain backgrounds forgive; busy ones do not
Erasing old text means synthesising the background that was behind it. Over a flat colour, a soft gradient, or a subtle paper texture, that fill is invisible. Over foliage, fabric folds, or a photograph of a crowd, the fill has to invent detail, and invention is where smudges appear.
If your text sits on busy imagery, draw the box tight around the line and keep expectations realistic: the result will be usable, the edges may need a second pass.
3. Keep the replacement the same kind of letterform
The tool estimates size, colour and spacing from the pixels it erased, then renders with an open-source font of matching character — a condensed grotesque stays condensed, a bold slab stays bold. What it cannot do is reproduce a distinctive display face or hand lettering.
Short swaps — a date, a price, a venue — hide this well because the eye reads the line, not the glyph shapes. Replacing a three-word headline with a full sentence of calligraphic script will not convince anyone.
4. Character count drives the spacing more than the font does
The new text is laid out to fit the width it was given. A replacement of similar length keeps the rhythm of the original. A replacement twice as long gets tighter tracking, and at some point the layout starts to look squeezed.
If the new copy is much longer, consider editing a shorter fragment of the line rather than the whole line.
5. PNG in, PNG out
Upload the highest-quality file you have. If the original is a JPEG, the text edges already carry compression artefacts, and the re-rendered text will sit next to them — visible at close range.
The download is always a PNG at the original pixel dimensions, so the file is suitable for print output at the same DPI you started with. Nothing is resampled on the way through.
