How do I increase the font size of a table in PRTG's Maps?

How can I increase the font size of the alarms table in a PRTG map embedded via iFrame, since the default font is too small and I couldn't find a clear option in the CSS files?

It is possible to add the font size directly to a map object. You find all map objects in the \webroot\mapobjects subfolder of your PRTG directory. Open the desired map object with an editor and add the font to the style statement, for example:

<div class="top10listcontainer" style="overflow:hidden;font-size:24px">

Save the adjusted html code as a custom map object (as an extra html file) in the \mapobjects folder so that PRTG does not overwrite it. Then you can use this object in your maps.

See also How can I add or edit map objects used for PRTG's maps?

Note: It is not possible to change the font size for a Sunburst map object because it is already adaptive.

You can change the <installation folder>\webroot\css\styles_custom.css and for example add

.customalarms_biggerfont td {
    font-size: 30px !important;
}

Afterwards create a new map object, and add the new css class in the second line of the object. For the Alarm Table, the object might look like this:

<!--Data Tables: Custom Alarms-->

<div class="map_object map_table customalarms_biggerfont" id="<@itemid>" objectid="<@objectid>" subid="<@subid>" style="overflow:auto;<#mapobject type="coordinates" subid="<@subid>" mode="<@editmode>">">
  <#mapobject type="objectgrip" mode="<@editmode>">
  <#mapobject type="htmlbefore" subid="<@subid>">
  <#checkobjecttype objecttype="probenode,group,device" nicemessage="true" id="<@objectid>">

  <div class="maptablecontainer" style="overflow:hidden">
    <#lang key="html.mapobjects.tablea0.tabletitle" default="Alarms (@@@@)" var="tabletitle">
    <#table tableid="sensortable"
    id="<@objectid>"
    content="sensors"
    columns="downtimesince,sensor,status,lastvalue,probegroupdevice,message"
    sortby="downtimesince"
    infoheader="false"
    links="false"
    sortable="false"
    varexpand="tabletitle"
    tabletitle="@tabletitle"
    filter_tags="@tag(<@tagfilterstring>)"
    filter_status="5"
    filter_status="4"
    filter_status="10"
    filter_status="13"
    filter_status="14"
    >
  </div>
  <#mapobject type="htmlafter" subid="<@subid>">
</div>

Store this object in the directory <installation folder>\webroot\mapobjects

Please note, that you might need to clear the browser cache for those changes.