Blog

Guides and tutorials for exploring data in your browser.

Cleaning

Fixing messy, inconsistent, or broken data.

5 min read

A Complete Guide to Handling NULL and Empty Values

Understand the difference between NULL, empty strings, "N/A", and "null" and handle each one consistently.
5 min read

How to Standardize Inconsistent Company Names in a CSV

Fix variations like "IBM", "I.B.M.", and "International Business Machines" using Find & Replace and Bulk Replace.
4 min read

How to Remove Test Data and Junk Rows from a CSV

Filter out TEST rows, placeholder emails, and zero-value entries using the condition builder.
4 min read

Converting "$1,234.56" Strings to Actual Numbers

Strip dollar signs and commas, then convert to a numeric type you can sum and filter.
5 min read

Fixing Dates When Your CSV Has Three Different Formats

Normalize MM/DD/YYYY, Jan 15 2024, and ISO dates into one consistent date type.
4 min read

Converting Yes/No/True/False/1/0 to a Consistent Boolean

Group all truthy and falsy variations into a consistent boolean column.
5 min read

Splitting a Full Address into Street, City, State, Zip

Break apart single-column addresses into separate fields for geographic analysis.
5 min read

Fixing Messy Phone Number Formats in Your Data

Standardize phone numbers from 8+ formats into one consistent format.
5 min read

Finding Near-Duplicate Rows in Your Data

Normalize text, then deduplicate records that differ only by case, spacing, or abbreviations.
4 min read

Extracting Email Domains to Identify Company Accounts

Pull the domain from email addresses to segment users by company.
4 min read

Filling Missing Category Labels Using Forward Fill

Fix report data where category names only appear on the first row of each group.

Exploring

Understanding your data, finding patterns, and filtering.

5 min read

What to Do First When You Open a New CSV File

A systematic approach to understanding an unfamiliar data file in under 5 minutes.
5 min read

How to Find Outliers in Numeric Data Without Code

Spot suspicious values using histograms, top/bottom filters, and summary statistics.
4 min read

Understanding Category Distributions in Your Data

See how many records fall into each category and find dominant groups or misspelled values.
5 min read

Checking Date Ranges and Gaps in Time Series Data

Verify your data covers the expected date range and find missing weeks or months.
5 min read

Finding Patterns in Missing Data

Discover whether missing values are random or systematic - by date, category, or source.
5 min read

Comparing Two Versions of the Same Data File

Find new rows, deleted rows, and changed values between two exports using a FULL JOIN.
4 min read

Quick Top-10 Analysis: Finding the Biggest Items

Find top customers, most common categories, or highest values in 30 seconds.
5 min read

Opening and Exploring JSON Files as Tables

Load JSON or JSONL files, flatten nested objects, and browse API responses visually.
5 min read

Spotting Columns Where the Data Type is Wrong

Identify numbers stored as text, dates as strings, and other type mismatches.
4 min read

Working with Large Files: Sampling and Limiting Rows

Explore multi-million row files efficiently by limiting, filtering, or sampling.
4 min read

Creating Charts and Visualizations from CSV Data

Build bar charts, line charts, and more from your data using the built-in Chart Builder.

Transforming

Reshaping, converting, and computing new values.

4 min read

Adding a Calculated Column to Your CSV

Create profit from revenue minus cost, totals from quantity times price, and other computed columns.
5 min read

Calculating Percentages and Ratios Across Columns

Calculate what fraction of total revenue each product or region represents.
4 min read

Adding Running Totals and Cumulative Sums

Add a column that accumulates values over time for revenue tracking or reconciliation.
5 min read

Ranking Rows by Value: Top Salespeople, Best Products

Assign rank numbers with ROW_NUMBER, RANK, and DENSE_RANK, including per-group ranking.
5 min read

Creating Conditional Columns: If-Then Logic Without Code

Add "High", "Medium", "Low" tier columns based on revenue thresholds or custom rules.
5 min read

Extracting Data From Messy Text Columns

Pull product codes, invoice numbers, or IDs out of free-text descriptions.
4 min read

Doing Math Across Columns: Add, Multiply, Round

Calculate tax, apply discounts, convert units, and round results.
4 min read

Remapping Category Codes to Readable Labels

Replace "CAT_01" with "Electronics" and "REG_NE" with "Northeast" using Bulk Replace.
4 min read

Splitting Multi-Value Cells into Separate Rows

Turn "electronics, sale, featured" in one cell into three separate rows.
4 min read

Combining First Name and Last Name into Full Name

Merge two name columns into one for mailing lists or reports.
5 min read

Extracting Fields from JSON Columns into Regular Columns

Parse a JSON metadata column into separate, typed columns you can filter and sort.
4 min read

Copying a Column and Transforming the Copy

Keep the original intact while creating a normalized version alongside it.
4 min read

Calculating Age from a Date of Birth Column

Turn a birthdate column into current age in years using Date Difference.

Advanced

Window functions, joins, SQL, JSON, and AI features.

6 min read

Window Functions Without Writing SQL: A Visual Guide

Understand ROW_NUMBER, RANK, running totals, LAG, and LEAD through visual examples.
5 min read

Building Complex Filters with AND, OR, and NOT

Combine multi-condition filters with nesting, type-specific operators, and keep/remove modes.
5 min read

Building a Multi-Step Data Pipeline

Chain operations into a reproducible pipeline with editable, reorderable steps.
5 min read

Using AI to Generate SQL Queries for Your Data

Describe what you want in English and get DuckDB SQL back from Claude.
6 min read

DuckDB SQL Cheatsheet for CSV Analysis

Quick reference for aggregations, string functions, dates, window functions, and more.
5 min read

Analyzing Data Across Multiple Files

Load multiple CSVs, join them, and build cross-file analysis pipelines.
4 min read

Converting Between CSV, Parquet, JSON, and Excel

Open any format and export as another. Clean your data before converting.
4 min read

Finding the Nth Largest or Smallest Values

Find the 3rd highest salary, 5th lowest price, or any Nth extreme value.
5 min read

Using Regex to Extract Patterns from Text

Pull zip codes, invoice numbers, or any pattern using regular expressions.
4 min read

Using Multiple Views to Compare Transformations

Create parallel analysis branches without losing your current pipeline.
5 min read

Grouping and Aggregating Data: A Practical Guide

Use the Group & Aggregate operation to compute SUM, AVG, COUNT, and more across grouped rows.
5 min read

Extracting Tables from PDF Files in Your Browser

How PDF table extraction works, what types of PDFs produce good results, and tips for cleanup.
4 min read

Working with XML Data: Import, Explore, and Convert

Import XML files, flatten nested elements into columns, and export as CSV or JSON.
3 min read

Exporting Data as a Self-Contained HTML Table

Generate a standalone HTML file with your data table. Opens in any browser, no dependencies.

Workflows

End-to-end scenarios chaining multiple operations.

6 min read

Convert a Bank Statement PDF to CSV or Excel

Get transactions out of a statement PDF without uploading it anywhere, then reconcile the totals.
5 min read

Building a Monthly Sales Report from Raw Transactions

Turn flat order data into a summary by month, product, and region.
5 min read

Segmenting Customers by Purchase Behavior

Create customer tiers based on total spend, frequency, and recency.
5 min read

Cleaning and Normalizing a CRM Export

Fix messy names, remove duplicates, fill gaps, and trim a Salesforce or HubSpot export.
5 min read

Merging Survey Responses with Respondent Data

Join survey exports with your customer database to analyze by company or tier.
5 min read

Analyzing Expense Reports for Policy Violations

Flag over-limit expenses, weekend charges, and duplicate submissions.
5 min read

Reconciling Two Inventory Lists

Compare system counts against physical counts to find discrepancies.
5 min read

Calculating Time-to-Resolution from Support Tickets

Measure resolution time and analyze by priority, category, and assignee.
5 min read

Cleaning an Email Marketing List Before a Campaign

Remove duplicates, fix formatting, filter fake addresses, and segment by domain.
5 min read

Tracking Customer Cohorts by First Purchase Month

Build a cohort retention table to track how many customers return each month.
5 min read

Preparing Data for Migration to a New System

Reformat, rename, reorder, and type-convert columns to match a target schema.
5 min read

Parsing and Analyzing Server Log Files

Extract timestamps, log levels, and service names from raw log entries.
5 min read

Comparing Year-To-Date Financial Data Across Years

Find which products or regions grew by comparing this year vs. last year.
4 min read

Summarizing Sales Data by Region and Product Category

Import, filter, group, and aggregate order data into a regional summary. Export to Excel.
4 min read

Converting PDF Invoices to a Clean Spreadsheet

Extract line items from PDF invoices, clean up the data, and export as Excel.