Arc Sidebar Items

Overview

Arc's sidebar replaces the tab strip and the bookmarks bar. Each Space has two sections, and each profile has a row of Favorites:

All three are stored as items in StorableSidebar.json, not in Chromium's Bookmarks file. Each item records its URL, the page title, any title the user set, when it was created, and when it was last active. The sidebar can therefore show what a user had open and kept, with timestamps, independently of browsing history.

File Locations

Item Structure

Items sit in the items array of the main sidebar container (the object after {"global" : {}}, see Spaces). Like the rest of the file, items alternates ID strings and item objects:

"items" : [
  "641CE573-48C7-417F-B014-7E45BE994A4C",
  {
    "id" : "641CE573-48C7-417F-B014-7E45BE994A4C",
    "parentID" : "87DC5386-D5EE-4447-AE0A-CE7E33E3128F",
    "childrenIds" : [ ],
    "title" : null,
    "createdAt" : 746426747.510035,
    "isUnread" : false,
    "originatingDevice" : "24564BF1-21DC-43F4-B69A-6991DBCCA1B0",
    "data" : {
      "tab" : {
        "savedURL" : "https:\/\/www.alfredapp.com\/help\/workflows\/inputs\/script-filter\/json\/",
        "savedTitle" : "Script Filter JSON Format - Alfred Help and Support",
        "timeLastActiveAt" : 746426762.639586,
        "savedMuteStatus" : "allowAudio",
        "activeTabBeforeCreationID" : "0604BE08-EC6A-4C41-A343-FB6BCD82649C"
      }
    }
  },
  …
]

Item Types

Resolving an Item's Section

An item does not record its section directly. Follow parentID upward, through any folders, until you reach a root itemContainer. Then identify that container:

1. If a Space's containerIDs (or newContainerIDs) lists it under pinned or unpinned, the item is in that Space's Pinned or Today section.
2. If topAppsContainerIDs lists it, the item is a Favorite of that profile.
3. Otherwise, its containerType.spaceItems._0 still names the owning Space.

If parentID is missing, look for the item in another item's childrenIds. Folder titles passed on the way up give the item's folder path.

Timestamps

Both are Mac absolute time: seconds since 2001-01-01 UTC. Add 978307200 for Unix seconds.

Manual Analysis

List every tab with its Space, section, title, URL, and last-active time:

jq -r '
  .sidebar.containers as $c
  | ($c | to_entries | map(select(.value | type == "object" and has("global"))) | .[0].key) as $g
  | $c[$g + 1] as $main
  | ($main.items | map(objects) | map({key: .id, value: .}) | from_entries) as $items
  | ([ $main.spaces[] | objects | . as $s
       | (.containerIDs // []) as $ids
       | range(0; $ids | length; 2)
       | {key: $ids[. + 1], value: {space: $s.title,
           section: (if $ids[.] == "pinned" then "pinned" else "today" end)}} ]
     + [ $main.topAppsContainerIDs | range(1; length; 2) as $i
       | {key: .[$i], value: {space: "", section: "favorites"}} ]
     | from_entries) as $roots
  | def root($id): if $roots[$id] then $roots[$id]
                   elif $items[$id].parentID then root($items[$id].parentID)
                   else {space: "", section: "unknown"} end;
    $items[]
  | select(.data.tab)
  | root(.parentID) as $r
  | [ $r.space, $r.section,
      (if (.title // "") != "" then .title else .data.tab.savedTitle end),
      .data.tab.savedURL,
      ((.data.tab.timeLastActiveAt // 0) + 978307200 | todate) ]
  | @tsv' \
  ~/Library/Application\ Support/Arc/StorableSidebar.json

This recipe reads containerIDs only. For files that have only newContainerIDs, adapt it to match enum labels.

Archived Tabs

When Arc archives a Today tab (automatically after 12 hours by default, configurable by the user), the tab moves to StorableArchiveItems.json. That file has the shape {"version" : 1, "items" : [id, {…}, …]}. Each entry holds:

Archived tabs hold recently closed browsing with exact archive times, a useful complement to History.

Analysis Notes

• Intent. A pinned tab took a deliberate action to create. Pinned and Favorite URLs are stronger evidence of regular use than a single history visit.
• Custom titles. A user-set title that differs from savedTitle is the user's own label for the page and can reveal how they thought about it.
• Folder paths. Folder names (e.g. "Clients / Acme / Contracts") add context to the URLs inside them.
• Multiple devices. Different originatingDevice values show items created on another Mac and synced in through Arc Sync.
• Unknown types. Arc adds new item types over time. Treat an unfamiliar data key as data to examine, not noise.

What macfor Collects

The browser.arc plugin emits one arc_sidebar_item record per tab, folder, split view, easel, or note in every sidebar container (main, Little Arc, and standalone windows), from the live file and every backup:

References

• Spaces — file structure and profile mapping
• arc-export — open-source StorableSidebar.json parser
• arc-oss: Arc sidebar format notes