Create a test file in your browser

Write a blank file or open a starter with syntax highlighting, format-aware preview, conversions, and direct download.

Best for

JSON, CSV, Markdown, HTML, XML, YAML, code, manifests, and archive members

The editor opens as untitled.txt; use New to switch to any starter without losing the local-first workflow.

Choose a format and bounded row or field settings, preview the result, then download a real data file locally.

Best for

CSV, TSV, JSON, JSON Lines, YAML, XML, HTML tables, and SQL inserts

The recipe workspace generates structured output; the source editor remains available for hand-authored test cases.

Select a verified Python recipe and generate a bounded synthetic test file in a temporary browser worker.

Best for

Text and data, archives, image formats, WAV audio, and background-removal pairs

Python loads only after Generate is pressed. These fixed recipes supplement catalog samples; they do not recreate every specialized profile.

Build bounded ZIP, TAR, TGZ, or single-file GZ fixtures from editable text members and verify every output.

Best for

Nested paths, Unicode names, empty archives, and many small files

ZIP and TAR work without a compression codec. TGZ and GZ require browser compression streams and report when unavailable.

Build fields and validation from scratch, preview in a sandbox, and export standalone HTML, JSON, or a fillable PDF.

Best for

Autofill, scraper, validation, form-parser, and AcroForm fixtures

Structured fixtures keep their real sections and locked SAMPLE markings when opened in the Studio.

Compose headings, paragraphs, lists, key/value blocks, and tables with a live preview and multi-format export.

Best for

Letters, reports, invoices, spreadsheets, handouts, and print-ready drafts

Export HTML, Markdown, DOCX, XLSX when the document has a table, or print to PDF.

Edit real scene nodes: copy, tables, colours, shapes, logos, product images, and backgrounds, then export locally.

Best for

Product cards, social graphics, signage, stream frames, schedules, and branded layouts

The blank canvas and every published template use the same validated scene editor, local draft store, and export path.

Create bounded image outputs and paired background-removal fixtures with a local browser canvas.

Best for

PNG and JPEG output, browser-checked WebP, transparent cutouts, and alpha masks

WebP availability depends on the browser; the workspace checks the output instead of changing the extension of another format.

Synthesize a tone, frequency sweep, seeded noise signal, or silence and encode a bounded test fixture in a dedicated worker.

Best for

WAV, AIFF, AU, MP3, AAC, M4A, M4R, FLAC, AC-3, Ogg, and Opus fixtures

Versioned recipes and source/output SHA-256 hashes distinguish byte-identical paths from content-equivalent browser codecs.

Render a short geometric test pattern and encode it through the codecs this browser reports for the selected container.

Best for

MP4, M4V, MOV, MKV, WebM, CMAF, MPEG-TS, and HLS interoperability fixtures

No camera or microphone is requested. WebCodecs output is content-reproducible, but encoder bytes can differ by browser and hardware.