Data integrity for your surveys
How Mapster Prevents
Duplicate Survey Submissions
Learn how Mapster detects and prevents duplicate survey responses to keep your data clean and reliable.
When collecting survey responses, duplicate submissions can skew your data and lead to inaccurate insights. Mapster uses two methods to detect and prevent duplicates: IP Address detection and Respondent ID. Each method has its strengths and limitations.
Method 1: IP Address
What is an IP address?
An IP address is a unique string of numbers assigned to every device connected to the internet. It acts as an address that allows data to be sent and received between devices on a network.
How it works
When a respondent submits a survey, Mapster records a hashed version of their IP address. The raw IP is never stored. If the same IP submits another response to the same survey, Mapster flags it as a potential duplicate and blocks the submission.
Limitations
Shared networks
People in the same office, school, or household often share the same public IP address. IP-based detection could flag separate respondents on the same network as duplicates.
VPN and network switching
Respondents can avoid detection by switching networks (e.g., from Wi-Fi to mobile data) or using a VPN, which changes their IP address.
Method 2: Respondent ID
What is a Respondent ID?
The Respondent ID is a Universally Unique Identifier (UUID v4) - a random string automatically assigned to every new respondent. It contains no personal information, just a random identifier.
How it works
The Respondent ID is stored in the respondent's browser (local storage). When they attempt to submit another response to the same survey, Mapster checks for the existing ID and blocks the duplicate submission.
Limitations
Different browsers or devices
Since the ID is stored in the browser, respondents can bypass this check by using a different browser or device (e.g., desktop vs. phone).
Incognito / private mode
Incognito or private browsing mode does not persist local storage, so the Respondent ID is lost when the session ends, allowing a new submission.
Clearing browser data
If a respondent clears their browser's local storage or cookies, the Respondent ID is removed and they can submit again.
Comparison
| IP Address | Respondent ID | |
|---|---|---|
| Detection method | Server-side (hashed IP) | Client-side (browser storage) |
| Works across browsers | Yes | No |
| Works in incognito | Yes | No |
| Shared network safe | No | Yes |
| VPN bypass | Can be bypassed | Not affected |
| Clearing browser data | Not affected | Can be bypassed |
| Privacy | IP is hashed, never stored raw | Random UUID, no personal data |
Privacy
Mapster takes respondent privacy seriously. Both duplicate prevention methods are designed to minimize data collection:
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IP addresses are hashed before storage. The raw IP is never saved and cannot be recovered from the hash.
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Respondent IDs are random UUIDs with no connection to personal information. They exist solely for duplicate detection.
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No tracking across surveys. Duplicate detection is scoped to individual surveys. A respondent's data from one survey is never used to identify them in another.
Have questions? Contact us.