Contact
There is no support queue and no ticket number. Mail goes to the person who wrote the converter you are asking about.
A file that will not convert
The useful thing to send is the format and roughly how the file was made — "HEIC straight off an iPhone 15", "a PDF exported from Illustrator" — plus whatever the page said when it failed. Every error on this site is written to name the actual cause, so quoting it back is usually enough to identify the bug.
Please do not attach the file. Nothing you convert here is ever uploaded, and that would not be much of a promise if the support address were the exception. If a file is the only way to reproduce something, say so and we will work out a way that does not involve sending it.
Your privacy choices
Withdrawing consent, or asking what has been collected, does not need email — the privacy page explains what there is, and the Privacy choices link in the footer reopens the consent dialog on any page. If your browser sends a Global Privacy Control signal, analytics is already off and advertising is already restricted before either one loads.
If you would rather ask a person, that is what the address below is for, and it reaches someone who can actually act on it.
Something wrong on a page
Corrections are welcome and get made. The pages here quote measured numbers — file-size ceilings, what a conversion costs in quality, which metadata is dropped — and a number that has drifted out of date is worth more to us than a compliment.
How to reach us
Expect a reply in days rather than hours. This is not a company with a rota.