When the survey link is distributed via email, it is important that the message includes at least the following:

A clear heading in the subject line
A description of what the survey is about
The respondent is to understand why they are being invited to take part in the survey
Who is responsible for the survey, including contact details (email and telephone) and who the respondents can turn to if they have questions about the survey

If instead, the survey is distributed via a survey link published on a web page, the corresponding information is to be placed so that the respondents read through the text before they click on the survey link.