Guide Conversion de Formats

Free CSV · XML · JSON · HTML · Markdown No signup · No data stored · Works offline

Outils dans ce guide

CSV Formatter & Validator
Format, validate and preview CSV data
CSV to JSON Converter
Parse CSV files to JSON objects
JSON to CSV Converter
Export JSON arrays as spreadsheets
XML Formatter & Validator
Format and validate XML documents
XML to JSON Converter
Convert XML attributes and elements to JSON
JSON to XML Converter
Convert JSON to well-formed XML
HTML to Markdown Converter
Migrate HTML content to Markdown
JSON Formatter & Validator
Format, validate and minify JSON
Last updated: March 2026  ·  v1.0
Quick Answer
How do you convert between CSV, XML, JSON, HTML and Markdown?

Each format conversion has different rules and edge cases. The 5 most important things to know:

  1. CSV to JSON: first row becomes keys; use RFC 4180 quoting for commas inside fields.
  2. XML to JSON: attributes map to @key; repeated sibling tags become JSON arrays.
  3. JSON to CSV: nested objects must be flattened using dot notation (e.g. address.city).
  4. HTML to Markdown: tables, bold, links and headings convert cleanly; custom CSS and colspan do not.
  5. All conversions on this site run entirely in your browser — no data is uploaded to any server.

Data lives in many formats simultaneously. Your database exports CSV, your legacy API returns XML, your frontend expects JSON, and your documentation platform needs Markdown. Moving data between these formats without errors requires understanding each format's rules and where they differ.

CSV to JSON: handling headers, types, and nested data

CSV (Comma-Separated Values) is deceptively simple, but real-world CSV files come with complications that trip up naive parsers.

Header detection: Most CSV files have a header row. Our CSV to JSON Converter treats the first row as keys for the resulting JSON objects. If your file lacks headers, add them before converting.

Type inference: CSV has no type system — every value is a string. A good converter infers types: 42 becomes a JSON number, true becomes a boolean. Our converter applies smart type inference while letting you override when needed.

Quoting and delimiters: Fields containing commas must be quoted. Fields containing quotes must escape them by doubling. RFC 4180 defines these rules. Tab-separated (TSV), semicolon-separated, and pipe-separated variants also exist — our converter auto-detects the delimiter.

XML to JSON: attributes, arrays, and namespaces

XML and JSON represent the same concepts differently. Understanding the mapping rules prevents data loss during conversion.

Attributes vs child elements: XML attributes have no direct JSON equivalent. The standard approach maps them to keys prefixed with @: {"@id": "42"}. Our XML to JSON Converter follows this convention.

Array detection: Multiple sibling elements with the same tag name are implicitly an array. Our converter detects this automatically.

Namespaces: XML namespaces are common in SOAP APIs and enterprise XML. The prefix becomes part of the key name in JSON.

Text content with attributes: An XML element with both text content and attributes maps to a special #text key for the text content.

JSON to CSV: flattening nested objects

Converting JSON to CSV requires making a two-dimensional table out of potentially multi-dimensional data.

Simple arrays: A JSON array of flat objects converts directly to CSV. Each object becomes a row, each unique key becomes a column.

Nested objects: {"address": {"city": "London"}} must be flattened. The standard approach uses dot notation: address.city becomes a column header. Our JSON to CSV Converter handles this with the Flatten nested option.

Arrays within objects: {"tags": ["js", "python"]} has no clean CSV representation. Options include joining values with a separator or using a separate CSV for the array.

HTML to Markdown: migrating content

Converting HTML to Markdown is common when migrating content between platforms — from a CMS to a static site generator, from a web scrape to a documentation tool.

What converts cleanly: Headings, paragraphs, bold/italic, inline code, code blocks, blockquotes, lists, links, and images all have direct Markdown equivalents.

What loses fidelity: Custom CSS classes, complex table layouts, nested lists deeper than two levels, and any semantic HTML that Markdown has no syntax for.

Tables: Standard HTML tables convert to GitHub Flavored Markdown (GFM) table syntax. Complex tables with merged cells cannot be represented in Markdown. Our HTML to Markdown Converter handles standard tables and normalises whitespace output.

Frequently asked questions about data conversion

Comment convertir un CSV de 100 000 lignes en JSON ?

Utilisez notre Convertisseur CSV vers JSON — il traite les fichiers côté client dans votre navigateur sans limite de taille de téléversement serveur. Pour les fichiers de plus de ~50 Mo, les outils en ligne de commande comme jq ou le module csv de Python sont plus efficaces.

Pourquoi ma conversion XML perd-elle des données ?

La cause la plus fréquente est la suppression des attributs XML. Assurez-vous que les attributs sont préservés dans le convertisseur. Vérifiez aussi les espaces de noms XML — les éléments comme ns:item deviennent des noms de clé littéraux en JSON.

Puis-je convertir un fichier CSV directement en XML ?

Pas directement avec un seul outil. Convertissez d'abord le CSV en JSON à l'aide de notre Convertisseur CSV vers JSON, puis convertissez le JSON en XML à l'aide de notre Convertisseur JSON vers XML. Deux étapes, le même navigateur, aucune donnée téléversée.

Pourquoi HTML vers Markdown perd-il ma mise en forme ?

Markdown est intentionnellement limité — il couvre 80 % des besoins de mise en forme courants. Le style CSS, les classes personnalisées et les mises en page complexes n'ont pas d'équivalent Markdown.

Quel est le meilleur format pour les réponses d'API ?

JSON est la norme pour les API REST. Il offre le meilleur support d'analyseur, la plus petite taille de charge utile pour des données structurées typiques, et un support natif en JavaScript. N'utilisez XML que pour les API SOAP ou l'intégration de systèmes d'entreprise hérités.