--- title: Card Formats description: card formats,wiegand,26-bit,h10301,corporate 1000,custom format,facility code --- [Skip to content](https://help.alocity.com/knowledge/card-formats#main-content) English Show submenu for translations [SUBMIT A TICKET HERE](https://help.alocity.com/knowledge/kb-tickets/new?hsLang=en) [![Alocity](https://help.alocity.com/hs-fs/hubfs/alocity-logo%20Full.png?width=181&height=48&name=alocity-logo%20Full.png)](https://www.alocity.com/) Open main navigation Close main navigation - English Show submenu for translations - [SUBMIT A TICKET HERE](https://help.alocity.com/knowledge/kb-tickets/new) - [Contact Support Now](mailto:support@alocity.com) [Contact Support Now](mailto:support@alocity.com) Hello. How can we help you? - There are no suggestions because the search field is empty. 1. [Alocity Help Center (Knowledge Base)](https://help.alocity.com/knowledge?hsLang=en) 2. [Mercury Installation, Setup And Configuration Guide](https://help.alocity.com/knowledge/mercury-installation-setup-and-configuration-guide?hsLang=en) 3. [Setup and Configuration](https://help.alocity.com/knowledge/mercury-installation-setup-and-configuration-guide?hsLang=en#setup-and-configuration) # Card Formats ## How to Choose the 8 Card Formats Your Mercury Controllers Read and Create Custom Formats A card format tells the controller how to decode the bits a card sends, such as the facility code and card number. Mercury controllers decode up to **8 card formats** at a time. The 8 slots apply to every Mercury controller in the account. --- ### 1. Open Card Formats Click **Settings** (⚙) › **Card formats**. There are two tabs: - **Active slots**: the 8 formats loaded on your controllers. - When the controller is online all formats can be read but only 8 can be locally stored on any panel during an Internet outage. ![Screenshot 2026-11-05 131821](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20131821.png?width=670&height=354&name=Screenshot%202026-11-05%20131821.png) - **Library**: **My formats** (custom formats you create) and **Market** formats (read-only). *![Screenshot 2026-11-05 132018](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20132018.png?width=670&height=363&name=Screenshot%202026-11-05%20132018.png)* > **IMPORTANT:** You can create as many custom formats as you need, but only the **8 formats in active slots** are loaded on the controllers. If a controller goes offline, it can only read cards in those 8 formats. Standard formats include Standard 26-bit (H10301), HID 37-bit (H10304 and H10302), HID Corporate 1000 (35-bit and 48-bit), 34-bit (N34), 32-bit and Aperio 40-bit. --- ### 2. Put a Format in a Slot 1. On the **Library** tab, open the format's menu and click **Use in slot…**. 2. Choose the slot to replace. 3. Click **Transfer to panels** to send the change to your controllers. > **IMPORTANT:** Replacing a slot stops controllers from reading that format. Check that no cards in use rely on it first. --- ### 3. Create a Custom Format 1. Click **Create custom format**. 2. Enter a **Name** and the **Total bits** (8–128). 3. Set the position and length of each data field: **Facility code**, **Card number** and, if used, **Issue code**. 4. Set the **Parity** bits. 5. Under **Advanced**, choose **Reverse bit order** or **Reverse byte order** if the card manufacturer specifies it. 6. Save, then put the format in a slot. *Note: If you make overlapping Bits by mistake, it will not let you save the card and the bits will be red and white indicating what is wrong.* *![Screenshot 2026-11-05 132132](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20132132.png?width=408&height=954&name=Screenshot%202026-11-05%20132132.png)* --- ### 4. Troubleshooting - Access logs show **Denied (Error in Card Format)**: the card's format isn't in an active slot. - Use the reader's **Test swipe** to see the format a card reports. See [Configuring Readers](https://help.alocity.com/knowledge/mercury-configuring-readers?hsLang=en). - Reader **Protocol** (Wiegand 26, Wiegand 34, OSDP Secure) is set per reader. See [Configuring Readers](https://help.alocity.com/knowledge/mercury-configuring-readers?hsLang=en). > **Note:** F3D100 and AI-1000 devices don't use these slots. Their Wiegand format is set on each device's Settings tab. See [Wiegand Input and Output Set-Up](https://help.alocity.com/knowledge/wiegand-input-and-output?hsLang=en). 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