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About Offline Surveys



Adding the CAPI sample source within the Survey Editor allows you to administer surveys and collect data with or without an internet connection using a web or mobile browser or the Decipher CAPI app found in the iOS & Android app stores. This is the perfect scenario for conducting research in areas where a network connection is unreliable or nonexistent. For example, you might create an offline survey to collect information door-to-door or from a booth at an outdoor event.

1: How it Works

To manage an offline survey, you use Decipher in the usual way to build, test, distribute, and report, but instead of distributing survey links directly to respondents, you distribute the links to interviewers who administer the survey from their device via the Decipher CAPI App.  

As the interviewer administers the survey, the application collects and stores responses to their browser or device. Once a network connection is detected, the application automatically uploads the data to Decipher. Data collection and reports are the same between online and offline projects.  

1.1: Interviewers and Data Collection

You can manage interviewers who will administer your offline survey from the "Offline" tab of the survey's Field Report. When an interviewer is added, a link to the offline application login page is automatically generated, which you will distribute to the interviewer when the survey is ready to launch.

Click here for more information about adding interviewers and accessing their login links.

The interviewer can use either the offline web application or the Decipher CAPI App to access the survey. Click here for more information on installing and using the Decipher CAPI App.

Once logged in, the interviewer can practice and then administer the survey when ready.

1.2: Data Collection and Reporting

Data collection / reporting is the same between online and multi-mode projects. However, there are two additional reporting elements for offline studies:

  • Each interviewer's progress can be viewed/tracked on the "Offline" tab of the Field Report.
  • From the vinterviewerID table in the reports, you can view interviewer performance.

2: Offline Surveys Supported Functionality

Some online survey functionality is not supported for offline surveys. The following sections outline the questions, elements, logic functions, and browsers currently supported for offline surveys.

Offline projects do not support survey attribute settings such as display, device or field settings. Options can be applied but will not be used. Click here for more information about project settings.

2.1: Supported Questions & Elements

Standard Questions

  • All with default settings

Dynamic Questions

  • Button Single Select (1-dimension only)
  • Button Multi Select (1-dimension only)
  • Image Upload
    • Respondents can capture photos via their mobile phones and upload or pull them from their libraries. Non-mobile users can upload via saved files on their desktops.
  • Video Testimonial
    • Respondents can record video testimonials and upload them.
  • Audio Testimonial (available only when using the CAPI app)
    • Respondents can record audio testimonials and upload them.

Structural Elements

  • Terminate, <term>
  • Skip, <goto>
  • Section, <label>
  • Autofill, <autofill>
  • Block, <block>
  • Loop, <loop>
  • Note, <note>
  • Finish, <finish>
  • If, <if>
  • Marker, <marker>

 Currently, survey themes are not supported in offline or multi-mode surveys. You can apply a theme using the Theme Editor, but the theme will not be used.

2.2: Supported Logic

Supported Logic

Attributes for all question types:

  • where
  • values
  • grouping
  • shuffleBy
  • randomize (shuffle)
  • optional
  • cond
  • rowCond / colCond / choiceCond
  • uses (only supports values atm1d.8, imgupload.1, videocapture.1, andaudiotestimonial.1)
  • sbase
  • alt
  • nets
  • sst
  • adim
  • percentages
  • ratingDirection (can be default, or reverse)
  • blankIfZero
  • fwidth
  • horizontalPercentages
  • translateable
  • type (can be none, or rating)
  • virtual
  • averages

Attributes for multi-select (<checkbox>) questions:

  • atleast
  • atmost
  • exactly

Attributes for number/float questions:

  • verify (number)
  • ignoreValues

Attributes for the terminate element:

  • markers

Attributes for the skip element:

  • target

Attributes for the block element:

  • randomizeChildren
  • count
  • randomize

Attributes for loop/looprow/loopvar elements:

  • randomizeChildren
  • builderSource

Attributes for cells:

  • value
  • size
  • optional
  • autofill (within checkbox elements)
  • exclusive (within checkbox elements)
  • randomize
  • open
  • openOptional
  • aggregate
  • chartText
  • indices (net)
  • labels (net)
  • pos (net)
  • values (net)
  • averages


  • Bracketed piping (e.g., [pipe: q1]), with all string transformations

Python expressions:

  • Python expressions (e.g., ${q1.r1.text})

Python semantics:



Cell access as an item


Cell access as attribute


Value access


Value setting

q1.r1.val = None

OE Value access


Answer selection confirmation


Question attributes

label, title, rows, cols, choices

Cell attributes

label, text, index

Question convenience methods and attributes

selected, check(), values, count, any, all

Exit page conditionals

qualified, terminated

Boolean operators

==, >, <, >=, <=, !=, in, not in, or, and, not

BitWise Operators

+, -, ~, *, /, %


any, all, True, False, None, list, dict, tuple, str, bool, float, int, print, if, else

Hermes methods and objects

hasMarker, setMarker, condition, res, p


2.3: Supported Browsers

Additionally, offline surveys are not supported on all internet browsers. See below for a list of currently supported browsers for offline surveys:


  • Chrome*
  • Firefox*


  • Android 6 Chrome*


  • iOS (version 9+, recommended 10)
  • Android (version 6+, recommended 6)

The asterisk character (*) indicates testing is performed in the current version of the browser.

3: FAQs

Here is a list of some frequently asked questions regarding our offline surveys and use of the CAPI app:

  • Q: Is the data that is transmitted from device to server encrypted?
    A: Yes. Data is transmitted from the device to the server using normal TLS encryption.
  • Q: Does your device have to be connected to the internet to login?
    A: Yes. Because we do not store user data on the device (e.g. username / password), the device must be connected to the internet in order for users to login to their Decipher account or to switch accounts on a single device. Similarly, surveys must also be downloaded to a device before going offline.
  • Q: Is there a safe amount of data that can be stored on the device?
    A: Respondent and survey data (survey questions, etc.) are stored together, and are limited to 2MB on iOS / 5MB on Android. Storage of images, video, and other media files is only limited by the space available on the device.
  • Q: Does uploading data to the server remove it from the device?
    A: Yes. Uploading data to the server from a device will remove it from the device.
  • Q: Is there a safe number of questions, elements, loops, etc., to add to a survey?
    A: There are many factors which can impact storage consumption and load times for an offline survey. For example, a survey with 10 open-ended questions could consume available storage at a faster rate than a survey with 100 single-select questions. We recommend testing the survey with simulated data and checking its resource usage prior to going offline. A summary of the available storage space can be found at the bottom of the app user menu.