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This document describes version 5 of Unblu. If you’re using the latest major version of Unblu, go to the documentation of the latest version.

The support period for version 5 ended on 22 November 2021. We no longer provide support or updates for this version. You should upgrade to the latest version of Unblu.


This is a compilation of frequently asked questions designed to give customers of our products some important answers quickly on a self-service basis.

The browser is slow or unresponsive

Q: What can I do if the browser does not respond or responds slowly?

A: You can do anything you would normally do: Click the back button, reload the page, wait, even temporarily go to another page. As long as you do not close the browser (that is, terminate the browser program), co-browsing will continue.


Q: I need a login, where can I get one?

A: Ask the product owner of your company, if you are working for a company that has an existing Unblu license. Otherwise, you can register at: - please note that the email address will be your username - do not use for example.

Dynamic snippet injection

Q: Can I add the snippet dynamically ?

301 error code accessing starter.js

Q: Why does starter.js return 301?

A: The "301 Moved Permanently" code is normal. While the starter.js request itself cannot (must not) be cached, it redirects to a path and content which is Unblu release-specific and contains maximum cache headers. As a result, the browser always has to request starter.js for each page. However, the resulting script only has to be requested once per customer visit.The redirected script is then stored in the browser cache and only downloaded again from the server when an update on the cloud has been performed.

Button control

Q: How can I control the buttons (activation element)?

A: State-dependent buttons are currently only supported by custom UI implementations based on the API. With the API you can define what buttons you would like to display, and consequently define the states. Details can be found in the documentation of the Unblu JavaScript API.

Positioning the UI control

Q: Is it possible to set the position of the control UI by custom coordinates?

A: Yes. You will find this and more in the Cloud Admin Application.

Support for Internet Explorer 8

Q: Is IE8 supported by Unblu?

A: No, Internet Explorer support starts at version 10.

PDF support

Q: Why can I, as a co-visitor (agent), not see a PDF document in my browser?

A: There are two ways you can access PDF files:

Co-browsing a PDF file requires Universal co-browsing

The PDF can be co-browsed in a Universal session, or in a combination of Universal and Embedded, by first starting in Embedded then switching to a Universal session.

For example, if the visitor, during an Embedded session, clicks a link leading to a pdf file, the file will either download or open in the visitor’s browser (depending on the browser the visitor is using). In this case nothing will happen on the agent (co-visitor) side.

Downloading the file

This requires file sharing to be enabled. File sharing means that any co-browsing participant can upload a file which can then be downloaded by all other participants.

To download a file:

  • In the Cloud: You must enable file sharing.

  • On premises: You must have either file sharing enabled or you must use the Unblu filter.

    When using the filter, in an On-premises installation, you can download pdf files without enabling file sharing.

To enable file sharing see Enable Or Disable File Sharing.

Timeout duration

Q: Timeout session is short. It would be nice to be able to get it parameterized. A: Unblu has multiple timeouts:

  1. One timeout defines the duration that a PIN can be used.

  2. Another timeout defines how long a co-browsing session is active when there is no action by any user.

Customer callback option

Q: The window asking for a PIN should also contain a field for the customer to enter a phone number that can be used to call him back.

A: If you would like to offer your customers a callback service you can implement your own user interface and control Unblu by using the API.

Support for Google Analytics

Q: Can activity be logged to the statistics on Google Analytics?

A: Yes, Google Analytics and other customer specific logging can be implemented by using the API.

PIN dialog customization

Q: Is it possible to customize the PIN dialog?

A: Only text and color can be customized. However, there is an option to build a custom user interface based on the API according to the design of your choice.

Browser "insecure" warning

Q: Why does my browser indicate a secure/insecure warning?

A: This should not be the case. Please contact to clarify.

Please take into consideration that, by default, images, CSS and other resources are transferred by the collaboration server from the origin server to the co-visitor. For this reason the server must have access to these resources. This is needed because our desk (co-visitor) is accessed through HTTPS, thus mixing HTTPS and HTTP causes the co-visitor browser to indicate a secure/insecure warning.

Co-visitor browser "insecure" warning

Q: How can I see all content of the page on the co-visitor browser when there is a secure/insecure warning?

A: This should not be the case. Please contact to clarify.

It is recommended to avoid mixed content. But if mixed content is used, the following applies:

  • IE8: On IE8 you get a popup warning asking you if only the secure resources of the page should be loaded. You can just click NO.

  • IE9: At the bottom of your browser you get a warning asking you whether to show all the content of the page. You should click on Show All Content.

  • Google Chrome: In the address bar you will see a shield icon on which you can click and then click on Load anyway.

Change the language of the Unblu UI

Q: Is it possible to configure Unblu to use a specific language? Is the language which Unblu displays only HTTP header language accepted, or is there another way to configure this?

A: Unblu uses the default behavior of the browser language and English as a fallback. If you want to support different regions and languages that differ from the browser language, e.g., when a user on an English-adjusted browser visits a German website and you want it to be in German. See Selecting the Language.

Supported language

Q: What languages are supported by Unblu?

A: There are many languages supported out of the box, e.g., English, German, Italian, French. If you want to support a language that is not shipped out of the box yet, you can provide us the texts available so that we can configure the language for you.

Requests to Unblu JavaScript

Q: Is there a request to the Unblu JavaScript for every page view?

A: Universal does not require the snippet on page load whereas Embedded co-browsing always requires the snippet on all pages. Normally, the script will load one time per visit; meaning that Unblu uses a strong caching mechanism, ensuring that revisited pages will load from cache.

View-and-point mode

Q: Is it correct that in 'View-and-Point' mode, the co-visitor’s clicks are visualized for the visitor?

A: Yes, the co-visitor cannot navigate or fill-in any form. However, clicks are visualized with little circles in the customer browser. In addition, the co-visitor can use the "Marker" to highlight available elements (input, pictures, links) for the customer.

Customize message upon terminating co-browsing session

Q: A message is displayed after the co-browsing session is terminated on both sides. Is it possible to customize this message (in appearance and text) to match customer requirements?

A: The message is displayed only on the client side. The texts are easily configurable by properties. The appearance can only be customized by using the API.

Confirmation dialog for co-browsing sessions

Q: Is it possible to have a confirmation dialog ("Do you really want to quit") before the co-browsing session is terminated?

A: During a 'join' (Embedded) session, both parties are able to terminate the session. During a 'show' (Universal) session only the agent can terminate the session.

Tab UI customization

Q: Is placement, text and design (color) of the tab possible?

A: Yes, there are some parameters to position the tab. To customize the look beyond the basic configuration, the API can be used.

Guessing the PIN code

Q: What happens if someone just tries out PIN codes without being invited to a co-browsing session?

A: It is very unlikely to guess the PIN code by trial and error. (See Guessing the PIN Code In addition, the codes are only valid for a limited time and the number of digits and types of characters can be adjusted.

PIN code reuse

Q: Is it possible to reuse a code?

A: No. The PIN can be used only once.

PIN validity

Q: The PIN code is only valid for a certain time. Is it possible to invalidate it, or to configure the timeout?

A: Yes, it is configurable for the on-premises version of Embedded. For Universal, it is preset.

Hardware requirements for the Unblu Collaboration Server

Q: What are the hardware requirements to run the collaboration server with in-house hosting?

Scaling Unblu

Q: How does Unblu scale?

A: Unblu can scale for about 2500 agents (based on 250 concurrent sessions) on a single multi-core server. Note that scaling becomes less linear when large files are shared. The way your system is set up can have a big impact. For example, Universal co-browsing is powered by Docker and scales differently from embedded co-browsing and 'chat'.

You should consult with your DB Admin to assess your needs. If you have any questions about scaling, do not hesitate to contact

Unblu in cluster environments

Q: Can I use Unblu in clustered environments?

"Page too complex" error message

Q: The message 'Page too Complex' is displaying. How do I fix this?

A: This may be a browser problem or a hardware deficiency or, more likely, it is because the DOM has 'too many' nodes. See DOM Capturing for more.