# YAML to CSV
Flatten a YAML list or mapping of records into CSV with a unioned column header. Nested keys become dot-paths. Runs in your browser, no upload.
## Run it
- **CLI:** `gizza tool yaml-to-csv "alice:
age: 30
city: Paris
bob:
age: 40
city: Berlin"`
- **Web:** https://gizza.ai/tools/yaml-to-csv/
- **Agents:** machine-readable descriptor (parameters JSON Schema) at https://gizza.ai/tools/yaml-to-csv/tool.json
## Inputs
- `data` — YAML _(field)_
- `delimiter` — Delimiter _(field)_
- `header` — Include header row _(field)_
- `array_mode` — Array handling _(field)_
- `quote_all` — Quote every field _(field)_
- `key_column` — Mapping key column name _(field)_
## Output
- CSV (text)
## Query parameters
Open the tool pre-filled and auto-run via URL:
- `data` — YAML
- `delimiter` — Delimiter
- `header` — Include header row
- `array_mode` — Array handling
- `quote_all` — Quote every field
- `key_column` — Mapping key column name
Example: `https://gizza.ai/tools/yaml-to-csv/?data=alice%3A%0A%20%20age%3A%2030%0A%20%20city%3A%20Paris%0Abob%3A%0A%20%20age%3A%2040%0A%20%20city%3A%20Berlin&delimiter=comma&header=true&array_mode=json"e_all=true&key_column=key`
---
## What this tool does
Turn a block of **YAML** into a **CSV** table you can open in a spreadsheet.
Paste a top-level **list of records**, or a **mapping** whose values are records,
and every record becomes one row. The header is the **union of every record's
keys**, in the order they are first seen, so rows that are missing a field simply
leave that cell blank instead of shifting columns. Nested mappings are flattened
to **dot-path** columns (`address.city`), and arrays are rendered the way you
choose. Everything runs in your browser — the YAML never leaves your device.
## How the shape is read
- **A list of records** — the common case. Each list item is a row:
```yaml
- name: Ada
age: 36
address:
city: London
- name: Bo
age: 40
```
becomes `name,address.city,age` with one row per person.
- **A mapping of records** — when the top level is a mapping whose values are
themselves records, each entry is a row and its key is kept in an extra column
(named by **Mapping key column name**, `key` by default):
```yaml
alice:
age: 30
bob:
age: 40
```
becomes `key,age` / `alice,30` / `bob,40`.
- **A single record** — a top-level mapping whose values are all scalars is
treated as one row (no key column).
## Options
- **Delimiter** — separate columns with a comma, semicolon, tab, or pipe.
- **Include header row** — turn off to emit data rows only.
- **Array handling** — `json` writes an array as one compact JSON string in a
single cell (`["a","b"]`); `joined` joins a scalar array with `, ` in one cell;
`columns` expands each element into its own dot-indexed column (`tags.0`,
`tags.1`).
- **Quote every field** — wrap all cells in double quotes, not just the ones that
contain a delimiter, quote, or newline.
- **Mapping key column name** — the header for the key column when the input is a
mapping of records; leave it blank to drop the key.
## Limits
- The whole document is parsed in memory, so extremely large files (tens of MB)
may be slow in a browser tab.
- Only the **top level** decides the shape: a list of records, a mapping of
records, or a single scalar mapping. A top-level scalar, or a top-level list of
scalars, has no columns and is reported as an unsupported shape.
- Deeply nested mappings flatten to dot-paths; if two different structures
produce the same dot-path, the later value wins.
- YAML anchors/aliases are expanded by the parser; custom `!tags` are dropped and
only their value is kept.
## FAQ
Is my data uploaded anywhere?
No. The conversion runs entirely in your browser with WebAssembly, so the YAML
you paste never leaves your device and the tool keeps working offline once the
page has loaded.
What happens when records don't all have the same keys?
The header is the **union** of every record's keys, in first-seen order. A record
that is missing a key just gets an empty cell for that column, so columns never
shift out of alignment.
How are nested objects and arrays handled?
Nested mappings are flattened to dot-path columns — `address: {city: London}`
becomes a column named `address.city`. Arrays follow the **Array handling**
option: kept as a compact JSON string, joined into one cell, or expanded into
`name.0`, `name.1` columns.
Which delimiters and quoting rules are used?
Pick comma, semicolon, tab, or pipe as the delimiter. Fields are quoted only when
they contain the delimiter, a double quote, or a newline (embedded quotes are
doubled), following the usual CSV rules — or turn on **Quote every field** to
quote everything.
Why do I get an "unsupported top-level YAML shape" error?
The converter needs records to build columns from. A top-level list of records or
a mapping of records works; a bare scalar (`just a string`) or a list of plain
scalars has no fields to become columns, so it is rejected with a clear message.
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