Flatten Nested JSON for Spreadsheets and CSV

API responses and app exports often look like nested JSON: a user object with an address inside, an order with a list of line items, metadata bags with uneven keys. Spreadsheets want the opposite — a rectangular table with one header row and consistent columns. Paste nested JSON into Excel and you get a mess; convert naively and nested fields disappear or turn into useless [object Object] strings.

Flattening is the bridge. This guide explains what flattening does, when to use it, and how to go from nested JSON to CSV or Excel using RividTech tools that run entirely in your browser.

What “flatten” means

Flattening turns nested paths into column names (or repeated rows) so every value sits in a cell. A field like customer.address.city might become a column named customer.address.city or customer_address_city. Arrays are the harder part: a list of tags might become multiple columns, a JSON string in one cell, or multiple rows — depending on the strategy and the tool.

The goal is not to preserve every nuance of the JSON document model. The goal is a table a human or a CSV importer can use.

When you should flatten

• Exploratory analysis in Sheets or Excel on API data.
• Sharing with non-developers who will not read raw JSON.
• Bulk import into systems that only accept CSV.
• Quick diffs of structured exports as tabular snapshots.

Skip flattening when the next consumer is another API or a document store that understands nested JSON — keep the structure and only format it for readability.

A practical workflow

• Validate and format. Start with JSON Formatter so you can see the shape and catch syntax errors early.
• Flatten. Run Flatten JSON to pull nested fields up into a flatter structure suitable for tabular export.
• Export a table. Convert with JSON to CSV or JSON to Excel. Prefer CSV for pipelines; Excel for human review.
• Clean if needed. After you have CSV, use Column Tools, Remove Duplicates, or Find & Replace the same way you would on any other export.

Nested objects vs arrays

Nested objects (one address per customer) usually flatten cleanly into dotted or underscored column names. Each parent record stays one row; depth becomes width.

Arrays (many line items per order) force a choice:

• One row per parent — array values packed into a single cell or several fixed columns. Simple, but hard to aggregate.
• One row per child — explode the array so each item is its own row, repeating parent fields. Better for analysis; more rows.

Know which shape your spreadsheet or importer expects before you settle on an approach. If the first flatten pass is too wide or too sparse, trim columns after export rather than hand-editing thousands of cells.

Common pitfalls

• Inconsistent keys across records. Optional nested fields create sparse columns. That is normal — empty cells mean “not present.”
• Very deep nesting. Extremely deep paths make ugly headers. Consider trimming the JSON to the subtree you care about first.
• Mixed types in one field. Sometimes a value is a string, sometimes an object. Flattening may coerce or drop structure; inspect samples first.
• Huge payloads. Browser memory is finite. Work on a sample, or split upstream, before flattening multi‑megabyte dumps.

Going the other way

Flat CSV back to JSON is the reverse problem: CSV to JSON produces an array of objects with one level of keys. Rebuilding deep nesting usually needs application code or a deliberate schema — column names alone rarely encode a full document tree. Flattening is easy to automate; “unflattening” to a rich domain model is a design task.

Privacy

API dumps can contain personal data, tokens, or internal identifiers. Doing flatten + export in the browser keeps that content on your machine. RividTech does not upload your JSON to process it — the same model described in Why Browser-Only CSV Tools Are Safer for Your Data.

Getting started

Format your payload with JSON Formatter, flatten with Flatten JSON, then export via JSON to CSV or JSON to Excel. From there you can preview, clean, or share a normal table — without ever sending the document to a server.