CSV Fill Down
Fill empty CSV cells with the last non-empty value above them (spreadsheet fill-down), or fill up from below. Choose which columns. Runs entirely in your browser, no upload.
CSV fill down
Fill empty cells in a CSV with the last non-empty value above them — the spreadsheet "fill down" you use to unflatten grouped or merged-cell exports. A cell counts as empty when it is blank or contains only whitespace. Switch Direction to up to back-fill from the next value below instead. It runs in your browser; nothing is uploaded.
Worked example
Input (grouped export where the repeated region was left blank):
region,rep
West,Ann
,
,Bob
East,
Fill down, all columns → output:
region,rep
West,Ann
West,Ann
West,Bob
East,Bob
Each blank inherits the nearest value above it in its own column.
Options
- Columns to fill — names (when there's a header) or 1-based indices, comma-
separated (
regionor1,3). Blank fills every column. - Direction — down carries the last value above into blanks below it; up carries the next value below into blanks above it.
- First row is a header — kept verbatim (never filled) and lets you name columns.
- Delimiter — comma, tab, semicolon, pipe, or any single character.
Limits & edge cases
- A blank at the very top of a column (fill down) or bottom (fill up) has no value to carry, so it stays empty.
- A completely empty line (no delimiters at all) is dropped by the CSV parser; a
row of empty cells (e.g.
,,) is kept and filled. - Values are copied exactly, including quotes and inner commas — the tool never reformats non-empty cells.
FAQ
What counts as an "empty" cell?
Any cell that is blank or contains only whitespace. Whitespace-only cells are trimmed and treated as empty, so a stray space still gets filled.
Can I fill only some columns?
Yes. Put the columns in Columns to fill as header names (region,rep) or
1-based indices (1,3), comma-separated. Any column you don't list keeps its
blanks. Leave the field empty to fill every column.
What's the difference between fill down and fill up?
Down copies the last non-empty value above a blank into it — the usual spreadsheet fill-down for un-flattening grouped rows. Up copies the next non-empty value below a blank into it, handy when a summary value sits at the bottom of a group. Pick one with the Direction control.
Does this fill blanks with a fixed value or an average?
No — it only carries forward (or backward) a neighbouring cell's own value. To
drop a constant like N/A into every blank, use a CSV cleaner instead; average
imputation is a separate numeric task and isn't done here.
Is my data uploaded?
No — it's processed locally with WebAssembly. Nothing leaves your browser.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool csv-fill-down "region,rep
West,Ann
,
,Bob
East,"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/csv-fill-down/?data=region%2Crep%0AWest%2CAnn%0A%2C%0A%2CBob%0AEast%2C&columns=region&direction=down&header=true&delimiter=%2CMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.