Highlight key data moments faster

Use a line highlight to add a vertical or horizontal reference line at a specific point on your chart. It’s useful for marking a single moment that helps explain the data, such as a product launch, policy change, price increase or major event.

In Flourish, the annotation string needs the label, axis value and optional color in the right order. Instead of writing that syntax yourself, describe the highlight you want and let the Assistant format it for you.

Add a vertical line highlight at 1974 labeled "First AI winter begins" in dark grey

Use a range highlight when you want to mark a period of time or a section of the chart, rather than one single point. It fills the space between two axis values with a colored band, which is useful for showing things like a recession, campaign period, product era or policy window.

Shade 1950 to 2000 with a grey fill, label it "Early compute", match the date format in YYYY-MM-DD, and set label max width to 30

Some charts need more than one annotation. If your chart covers a long timeline, you may want to mark several key periods, events or turning points so the story is easier to follow.

Instead of writing each annotation string one by one, describe all the highlights you want in a single prompt. The Assistant can generate the full set for you, with the right dates, labels, colors and formatting applied consistently.

Add three range highlights: 

“Pre-deep learning era” from 1950 to 2012 in light grey range with a grey label, 

“Deep learning era” from 2012 to 2020 in light teal range with a teal label, 

and “LLM era” from 2020 to 2026 in light pink range with a pink label. 

Ensure dates are formatted as YYYY-MM-DD, label max width is 30, each labels are strictly color-matched to their highlights, and labels are vertical.

If your chart is split into a grid of charts, you can add annotations to one small multiple at a time. This is useful when each panel shows a different category, and each category needs its own context.

Before you prompt the Assistant, make sure the grid layout is enabled and your category column is bound in the Grid of charts settings. Then describe which highlight should appear in which panel. The Assistant can write the panel-specific syntax for you, including the extra facet reference that tells Flourish where each annotation should go.

Add:
1. a range from 2012-01-01 to 2020-01-01 labeled “Modern deep learning era” on the Vision facet in light teal, 
2. a line at 2017-06-12 labeled “Transformer” on the Language facet in pink, 
3. a line at 2016-03-09 labeled “AlphaGo” on the Games/Robotics facet in yellow, 
4. and a range from 2020-01-01 to 2026-01-01 labeled “LLM era” on the Multimodal facet in light orange. 

Match label colors to each highlight, max label width 30.

Open any chart in the Flourish editor and choose the prompt that matches what you want to highlight.

Each prompt works on its own, and because the Assistant shows you the annotation syntax it creates, you can also use it to learn the format as you go. Run a prompt, review the output and you’ll start to recognise the pattern.