# Footnotes
Footnotes provide a way to annotate specific cells, columns, or other table parts with additional context without cluttering the main display. **Great Tables** manages footnotes as a system: marks are automatically sequenced, placed consistently, and matched to their explanatory text in the table footer.
# A Basic Footnote
Adding a footnote requires two things: the footnote text and a location specifier indicating where the footnote mark should appear. The [tab_footnote()](../reference/GT.tab_footnote.md#great_tables.GT.tab_footnote) method handles both, placing the mark at the targeted location and appending the text to the footer.
``` python
from great_tables import GT, md, loc
from great_tables.data import airquality
air_mini = airquality.head(5)
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Measured in parts per billion (ppbV).",
locations=loc.column_labels(columns="Ozone")
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
The footnote mark (a superscript number) appears next to the `"Ozone"` column label, and the corresponding text appears at the bottom of the table.
# Targeting Different Locations
Footnotes can be attached to many different parts of the table. The `locations=` argument accepts any of the `loc` specifiers that support footnotes. Here are some of the most common targets.
## Column Labels
Attaching a footnote to a column label is useful for clarifying units or methodology.
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Solar radiation in Langleys (cal/cm²), measured 08:00-noon.",
locations=loc.column_labels(columns="Solar_R")
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
## Body Cells
You can annotate specific data cells by targeting them with [loc.body()](../reference/loc.body.md#great_tables.loc.body).
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Highest temperature in this sample.",
locations=loc.body(columns="Temp", rows=[0])
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
## The Title or Subtitle
Footnotes on the table header can provide methodological notes or data source context.
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Data collected at a monitoring station in midtown Manhattan.",
locations=loc.title()
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
# Multiple Footnotes
You can add multiple footnotes to a single table. Each call to [tab_footnote()](../reference/GT.tab_footnote.md#great_tables.GT.tab_footnote) creates a new footnote with its own sequenced mark. The marks are numbered in the order they appear in the table (reading left-to-right, top-to-bottom).
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Mean ozone concentration, 13:00-15:00.",
locations=loc.column_labels(columns="Ozone")
)
.tab_footnote(
footnote="Maximum daily temperature in degrees Fahrenheit.",
locations=loc.column_labels(columns="Temp")
)
.tab_footnote(
footnote="Measurement device was recalibrated on this day.",
locations=loc.body(columns="Ozone", rows=[2])
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
Three footnote marks are placed in the table, and three corresponding notes appear in the footer, each with its sequential number.
# Footnotes Without a Mark
If you want to include explanatory text in the footer without attaching a mark to any cell, omit the `locations=` argument (or set it to `None`).
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(footnote="All measurements taken in New York City, 1973.")
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
This is useful for general notes that apply to the entire table rather than to a specific cell or label.
# Controlling Mark Placement
The `placement=` argument determines where the footnote mark appears relative to the cell content. The options are `"auto"` (the default), `"left"`, and `"right"`.
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote="Measured at ground level.",
locations=loc.column_labels(columns="Ozone"),
placement="left"
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
With `placement="left"`, the footnote mark appears before the cell text rather than after it.
# Using Markdown in Footnotes
Footnote text supports Markdown formatting through the [md()](../reference/md.md#great_tables.md) helper function. This lets you include emphasis, links, or other inline formatting in your footnotes.
``` python
(
GT(air_mini)
.tab_header(title="New York Air Quality", subtitle="Daily measurements, May 1973")
.tab_footnote(
footnote=md("Source: *Interactive Data Analysis* (McNeil, 1977)."),
locations=loc.title()
)
)
```
| New York Air Quality |
| Daily measurements, May 1973 |
| Ozone |
Solar_R |
Wind |
Temp |
Month |
Day |
| 41.0 |
190.0 |
7.4 |
67 |
5 |
1 |
| 36.0 |
118.0 |
8.0 |
72 |
5 |
2 |
| 12.0 |
149.0 |
12.6 |
74 |
5 |
3 |
| 18.0 |
313.0 |
11.5 |
62 |
5 |
4 |
|
|
14.3 |
56 |
5 |
5 |
Footnotes are a subtle but important tool for building informative tables. They let you add precision and context where it matters most, keeping the main table body clean while ensuring readers have access to the details they need. The automatic sequencing and placement system means you can focus on content rather than managing mark numbers manually.