What This Tool Does
Fill Blank Cells writes replacement data into blank cells in a pasted or uploaded table. It detects columns, lets you define which values count as blank, and applies the rule you choose for each checked column. Parsing, filling, and export are performed by the page's browser-side script.
Define Which Cells Count as Blank
Use Treat empty string as blank for truly empty fields and Treat whitespace-only as blank for fields containing only spaces or other whitespace. Add comma-separated values in Custom blank markers (comma-separated), such as NULL, NA, N/A, -, or None.
When Treat whitespace-only as blank is enabled, an empty string is also treated as blank, even if Treat empty string as blank is disabled. Only cells matching these settings are eligible for filling.
Choose a Fill Rule for Each Column
Columns are detected automatically after data is pasted or uploaded. Check each column you want to modify and choose one rule. Unchecked columns are left untouched.
- Constant value: uses the same replacement value for every eligible blank.
- Fill from previous row: copies the nearest non-blank value above. It can reset at a group change.
- Fill from next row: copies the nearest non-blank value below. It can reset at a group change.
- Group value: choose a group column and use the first, last, or most common non-blank value in that group.
- Sequence: set a start and step, with an option to restart per group.
- Formula: reference same-row columns with values such as
{Price} * {Qty}.
Parse Headers and Irregular Rows
First row is a header is enabled by default. Turn it off when the first row is data; the tool then names columns Column 1, Column 2, and so on. The parser detects comma, tab, pipe, or semicolon delimiters by sampling the first 25 lines.
Rows shorter than the most common row length are padded with empty fields. Extra fields are merged into the final field so the table uses that most common width.
How to Use Fill Blank Cells
- Paste CSV, TSV, or pipe-delimited data into Paste your table below, or drop/upload a CSV, TSV, or TXT file.
- Set First row is a header and the blank controls.
- Check each target column, choose a rule, and set its parameters.
- Review the automatically updated summary, preview, and change log.
- Review the summary, per-column results, Preview, and Change log.
- Use Export CSV for the filled table or the change-log export for the recorded changes.
Review Results and Export
After filling, the page shows summary counts, per-column results, a Preview, and a Change log. The preview highlights filled cells and renders up to 200 rows. The visible change log renders up to 500 entries, while its count shows the total number recorded.
Export CSV downloads the full changed table as the comma-delimited file filled-data.csv. The change-log button downloads the complete log as fill-blank-cells-changelog.csv.
Unresolved Cells and Type Detection
If a rule cannot resolve a value, the cell remains blank and is counted as unresolved. This can happen when a previous-row or next-row source is unavailable, or when a formula cannot be evaluated.
The tool classifies non-blank column values as integer, number, date, boolean, or string. Only sequence output gets special integer formatting for a detected integer column; other rule results use the supplied or referenced values.
Limitations and Processing Scope
- The on-page preview is limited to 200 rows, and the visible change log is limited to 500 entries.
- The exported change log contains all recorded changes.
- Filled data is always exported with comma delimiters.
- Delimiter detection samples only the first 25 lines, and irregular rows are padded or merged as described above.
- Parsing, filling, and export are performed by the page's browser-side script. The local implementation does not establish site-wide account, usage-limit, upload, or complete privacy policies.
- This tool fills cells that match your definition; it does not standardize existing markers. Use Normalize Null Values when you need consistent
NULL/NAmarkers.
Frequently Asked Questions
How is this different from Normalize Null Values?
Normalize Null Values only standardizes how missing-value markers are written - for example turning "N/A", "null", and "-" into one consistent marker - without adding new data. Fill Blank Cells goes further: it writes actual replacement data into blank cells using a rule you choose, such as a constant, the previous row's value, a group value, a sequence, or a formula.
What counts as a blank cell?
Use Treat empty string as blank, Treat whitespace-only as blank, and comma-separated custom markers such as NULL, NA, N/A, or -. When whitespace-only mode is enabled, an empty string is also treated as blank, even if the empty-string toggle is disabled. Only matching cells are touched.
Does this infer values automatically?
No. Every fill is driven by a rule you explicitly select for that column - constant, previous row, next row, group value, sequence, or formula. The tool never guesses a value on its own; if a rule can't resolve a value, the cell is left blank and counted as unresolved.
Can I see what changed before exporting?
Yes. The preview shows up to 200 rows with filled cells highlighted. The on-page change log shows up to 500 entries and displays the total count. Export the change log as CSV to get all recorded changes.