Comparison windows (A and B)

Comparison windows let you compare any two stretches of time on the chart without using the comparison menu. For example: the two weeks before a site change against the two weeks after.

How to use it

1. Hold Shift and drag across the chart. That marks Window A, your baseline.
2. Hold Shift and drag again. That marks a second window. The earlier of the two is always Baseline (A) and the later is Focus (B). The focus is the period you are examining; the baseline is what you measure it against.
3. The number cards and the table now show B compared with A. The dashed comparison line is replaced by two shaded areas, grey for A and violet for B. A chip under the controls names them: Focus B, dates, days against Baseline A, dates, days, with an x to clear them. The chart key and the line under the chart title use the same names.
4. Only two windows exist at once. A third Shift-drag replaces the oldest one.

No Shift key, or no mouse?

• Touch screens: press Mark windows above the chart. While it is on, every drag marks a window instead of zooming. Press it again to go back to zooming.
• Keyboard: Tab to the chart, press the left and right arrows to move to a date, then press W to mark a window that starts there. The first window is 14 days (4 weeks or 3 months on a weekly or monthly chart); the next one takes the same length as the first when Same length is on.

Keep the windows the same length (on by default). Use the Same length switch in the chip (it reads Free length when it is off). While it is on:

• Your second window automatically gets the same number of days as the first. As you move the pointer, a ghost of that length slides along, and a label tells you the dates. Click or let go to place it. A Shift-click is enough.
• On a daily chart, windows of a week or more snap so both cover the same weekdays. That matters because weekends get fewer visits, so a window with an extra weekend would look worse than it is. Hold Alt to turn the snap off.

Change a window after you place it

• Drag a window’s left or right edge to change its dates. With Same length on, the same edge of the other window moves by the same amount, so the lengths stay equal.
• Drag the label pill at the top of a window to move the whole window. With Same length on it snaps to matching weekdays (hold Alt to skip that).
• Press Escape while dragging to cancel.
• With the keyboard, Tab to a window’s pill. Left and right arrows move it one day, Shift plus an arrow changes the end, Alt plus an arrow changes the start.

Windows of different lengths. Turn Same length off and you can make A and B different lengths. The cards and table then compare daily averages, so a 14-day window is not unfairly compared to a 10-day one. A note beside the chip says so (Different lengths (14 days vs 10 days), so changes compare daily averages) and offers Match lengths to make them equal again. The baseline’s clicks and impressions are scaled to the focus length; CTR and position are never scaled.

Share them. The windows are part of the page address, so a copied link, a bookmark or a reload shows the same two windows. Same length is in the address too.

Good to know

• The pill on the chart shows the length, for example “A · 14d”. If the two lengths differ, the key above the chart shows a ≠ sign.
• The shaded area never blocks the chart. You can still hover, zoom and Shift-drag over it. Your Google update bands and notes stay where they were.
• A single window does not change the numbers. Only two do.
• Windows stay when you zoom or change the date range. A window outside the visible dates is simply not drawn.
• With two windows set, no option in the Compare control is selected. Choosing one of them clears the windows and goes back to that comparison.
• The Queries, Pages and Countries & devices tabs and the CSV export follow the windows too. Groups and Opportunities keep using the date range and comparison from the controls.
• Windows have to be inside the days we have data for. A window that would run past the last day is moved back to fit, keeping its length. On Free, a window that reaches back past 16 months is cut at that limit.

Plans. The same on Free and Pro.