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This article applies to: ML v7, ML8, MultiStore

Validation Of Viewstate MAC Failed Error Message

Validation of viewstate MAC failed error message occurs.

If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

Solution for ML8 and older:
This could be due to the hosting environment. Try backing up your current web.config file...and then look for this line near the bottom:

<machineKey validationKey="AutoGenerate" decryptionKey="AutoGenerate" validation="SHA1"/>

Try replacing that line with something like:

<machineKey validationKey="627BF72BB33AA8D28CA2C3E80920BA4DF0B726F97EEFBB0F4818350D63E6AFA380811F13ED1F086E386284654DB3"
decryptionKey="F40B6E5A02B29A181D2D213B5ED8F50B73CFCFD0CC56E137" validation="SHA1" />

or use a key generator like the one found here

Solution for ML9 and newer:
  1. Have your server host set Read/Write/Modify permissions on your site's {root} folder (where the web.config file is located)
  2. Go into the site's Admin Console and the Configuration - Site Configuration Wizard
  3. Set the feature "Set Static Machine Key:" to YES, and Submit
  4. Have the host set the permissions level back how they were before