> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datachecks.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Profiling

> Datachecks profiles your datasets using both statistical and semantic analysis to give you a complete picture of your data before and after migration.

Profiling runs automatically when a dataset is scanned. It combines statistical metrics with AI-powered semantic analysis to characterize your data, identify sensitive columns, and recommend masking strategies.

## Statistical profiling

Statistical profiling collects quantitative metrics about your dataset:

| Metric              | Description                                                                         |
| ------------------- | ----------------------------------------------------------------------------------- |
| **Row count**       | Total number of rows in the dataset, tracked over time to detect unexpected changes |
| **Column count**    | Number of columns and their data types                                              |
| **Null counts**     | Per-column null value counts used to power completeness validations                 |
| **Distinct values** | Cardinality metrics used to power uniqueness validations                            |
| **Distributions**   | Value distribution metrics surfaced in the health score                             |

These metrics feed directly into the dataset's health score and row trend charts visible in the [Assets](/assets/overview) overview tab.

## Semantic profiling

Semantic profiling uses AI to analyze a sample of values from each column and determine what kind of data it contains — beyond just the raw data type.

For each column, the profiler produces:

| Field                        | Description                                                                         |
| ---------------------------- | ----------------------------------------------------------------------------------- |
| **Data type**                | The storage type of the column (string, numeric, date, etc.)                        |
| **Semantic type (general)**  | Broad category — for example, `identifier`, `financial`, `contact`, `location`      |
| **Semantic type (specific)** | Precise type — for example, `email`, `phone`, `aadhar`, `pan`, `api_key`, `address` |
| **Sensitivity**              | How sensitive the column is — used to flag columns for masking                      |
| **Confidence**               | How confident the model is in its classification                                    |

Semantic profiling examines up to five sample values per column and is powered by an LLM prompt that evaluates naming conventions, value patterns, and domain context together.

## Sensitive column identification

Columns with a high sensitivity rating are automatically flagged as potentially containing PII or confidential data. These columns appear visually marked in the dataset view and are candidates for masking.

Sensitivity is assessed based on the semantic type detected — for example, columns identified as `email`, `phone`, `aadhar`, `pan`, `bank_account`, or `api_key` are treated as sensitive.

## Masking strategies

Once a sensitive column is identified, the profiler recommends a masking strategy. The following strategies are supported:

| Strategy                     | Description                                            | Example            |
| ---------------------------- | ------------------------------------------------------ | ------------------ |
| `keep_last_n`                | Mask all but the last N characters                     | `****9012`         |
| `keep_prefix`                | Keep the first N characters, mask the rest             | `AB*******`        |
| `mask_username_in_email`     | Mask the email username, preserve the domain           | `r***@example.com` |
| `numeric_random_same_length` | Replace digits with random digits, preserve separators | `+91-8234167890`   |
| `date_mask_parts`            | Mask year, month, or day portions of a date            | `****-08-15`       |
| `hash_sha256`                | Replace with a SHA-256 hash (optionally salted)        | `3a5b9f2c...`      |
| `tokenize_uuid`              | Replace with a random UUID                             | `f47ac10b-...`     |
| `none`                       | No masking applied                                     | —                  |

Masking is applied in the UI so that sensitive values are not displayed to users in shared workspaces. The underlying data in your database is not modified.

## When profiling runs

Profiling runs automatically when:

* A dataset is first discovered after connecting a datasource
* You manually trigger a **Rescan** from the Assets view

You can view the profiling results for any column from the dataset detail view.