Validate YAML Files Online
Validate YAML file structure in your browser. Check null counts, distinct values, and data types for every column — no upload required.
How to validate YAML files
- Drop your file onto the upload area. The report starts as soon as the file has loaded. There are no settings.
- Read the four summary cards: total rows, columns, null-heavy columns and all-null columns.
- Scan the Column Report table for each column's detected type, null count, percentage of nulls and number of distinct values.
- Check the warnings under the table. Columns that are entirely null are flagged in red and columns that are more than half null in amber.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A clinic exports a week of appointments before loading it into a reporting database. The analyst wants to know which fields are reliable before writing any queries.
Input (YAML)
- patient_ref: P-104
clinic: Eastside
appointment_date: '2026-06-02'
no_show: false
notes: null
- patient_ref: P-221
clinic: Eastside
appointment_date: '2026-06-02'
no_show: true
notes: Called to rebook
- patient_ref: P-104
clinic: Harbour
appointment_date: '2026-06-09'
no_show: false
notes: null
- patient_ref: P-318
clinic: null
appointment_date: '2026-06-11'
no_show: false
notes: null
- patient_ref: P-450
clinic: Harbour
appointment_date: '2026-06-11'
no_show: true
notes: nullSettings
- No settings. The report is generated when the file loads.
Result
| Column | Type | Nulls | % Null | Distinct |
|---|---|---|---|---|
| patient_ref | VARCHAR | 0 | 0.0% | 4 |
| clinic | VARCHAR | 1 | 20.0% | 2 |
| appointment_date | DATE | 0 | 0.0% | 3 |
| no_show | BOOLEAN | 0 | 0.0% | 2 |
| notes | VARCHAR | 4 | 80.0% | 1 |
The summary cards read 5 rows, 5 columns, 1 null-heavy column and 0 all-null columns. notes is flagged in amber at 80% null. patient_ref has 4 distinct values in 5 rows, which shows P-104 appears twice, so it cannot be used as a unique key. Distinct counts ignore nulls, which is why clinic shows 2 rather than 3.
Frequently Asked Questions
Does Validate change or download my file?
No. It only produces the on-screen report. Nothing is modified and there is no download.
What counts as a null-heavy column?
Any column where more than 50% of values are null. The Null-heavy card counts all-null columns too, so a column that is 100% null is included in both cards.
Do distinct counts include nulls?
No. Distinct counts only non-null values. A column with values A, B and some nulls shows 2.
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