Does the cell hierarchy survive OASIS to GDSII conversion?

Yes. Both formats describe the same hierarchical model, so an OASIS CELL becomes a GDS structure and a PLACEMENT becomes an SREF. Nothing is flattened.

What happens to OASIS repetitions?

All twelve repetition types are read. A placement repetition of type 1, 2, 3, 8 or 9 collapses to a single GDS AREF, with type 8's arbitrary lattice carried in the column and row step vectors. That path is deliberately uncapped, because an AREF costs constant memory however large the array is. Irregular repetition forms expand to individual elements instead, capped at 250 000 per repetition and 2 000 000 per file, with any truncation reported rather than silently swallowed.

What units does the converted GDSII file use?

Integer world nanometres. The OASIS START record states database units per micron, so world nanometres per database unit is 1000 divided by that figure. At the usual 1000 units per micron the result is byte-for-byte what parsing the equivalent GDSII would report.

Do text labels keep their size and font?

Yes, where the file carries them. An OASIS TEXT record has no size, font or justification field, so those ride as element properties. The reader resolves them in a second pass, which is what lets a label keep its size instead of being stamped with a default.

Is a compressed OASIS file supported?

Yes. CBLOCK-compressed files are read; the compressed blocks are flattened transparently while the record stream is walked, so compression is invisible to the conversion.

Is there a file size limit?

The conversion runs inside your browser tab, so your machine's memory is the real ceiling. The converter checks the file size before parsing, warns above roughly 50 MB and declines files beyond roughly 200 MB rather than risking an out-of-memory crash.

Is my OASIS file uploaded anywhere?

No. The conversion runs entirely in your browser using the same reader as the Glyph editor. There is no server to upload to, and your design data never leaves your machine.

Convert OASIS to GDSII

OASIS-to-GDSII conversion moves a layout between two formats that describe the same thing: a hierarchy of cells holding polygons, paths and labels on numbered layers. Both are lossless for that model, so this is one of the cleanest conversions in mask work. It runs entirely inside your browser — the file is read, converted and written locally, and there is no server to upload it to.

How to convert OASIS to GDSII

Drop your .oas or .oasis file onto the converter on this page. Compressed (CBLOCK) files need no special handling.
Pick GDSII as the target format.
Download the .gds file. Open it in the free Glyph editor if you want to inspect cells, layers or array placements before handing it on.

What survives and what changes

Aspect	What happens
Hierarchy	Preserved. A CELL becomes a GDS structure and a PLACEMENT becomes an SREF; nothing is flattened.
Uniform arrays	Placement repetitions of type 1, 2, 3, 8 or 9 collapse to a single GDS AREF — type 8's arbitrary two-vector lattice rides in the column and row steps. This path is uncapped by design: an AREF costs constant memory however large the array is, and capping it would silently delete most of a legitimate wafer-scale array.
Irregular arrays	Repetition forms that are irregular lists expand to individual placements or elements, capped at 250 000 instances per repetition and 2 000 000 elements per file. Truncation is reported, never silent.
Shapes	Rectangles, polygons, paths, the three trapezoid records, the 26-entry CTRAPEZOID shape table and circles are all read and converted to GDS boundaries and paths.
Units	The START record's unit is database units per micron; world nanometres per database unit is `1000 / unit`. At the usual 1000 units per micron this matches what parsing the equivalent GDSII reports exactly.
Text	The TEXT record carries string, layer, texttype and position. Size, font and justification ride as element properties and are resolved in a second pass, so a label keeps its real size rather than a default.
Compression	CBLOCK (raw DEFLATE) blocks are flattened transparently as the record stream is walked, so a compressed file converts exactly like an uncompressed one.
Other properties	A general OASIS property such as a cell offset, a bounding box, or a foreign tool's own property is decoded only to keep the record stream aligned, then discarded — the GDS model has nowhere to put it.
Malformed files	A modal field that a record needs but the file never set is treated as a malformed file and reported, rather than being carried over from an unrelated record and drawing geometry in the wrong place.
File size	GDSII stores coordinates as fixed-width integers where OASIS uses compact variable-length encoding, so the converted `.gds` is normally substantially larger than the `.oas` it came from. That is the formats' design difference, not a conversion loss.

Why OASIS and GDSII both exist

OASIS — the Open Artwork System Interchange Standard, published by SEMI as P39 — was designed in the early 2000s to store the same geometry as GDSII in far smaller files, using variable-length numbers, built-in repetition descriptions and modal state that lets a writer omit unchanged values. GDSII, decades older, remains the default handoff format between design tools and mask shops, which is exactly why this conversion is worth doing: the archive format and the handoff format are not the same file.

For the full comparison — origins, file size, compression, adoption and tool support — see GDSII vs OASIS. For the destination format's record structure, see the GDSII file format reference. Going the other way is GDSII to OASIS.

Open it in the editor

To check cells, array placements and layer assignments after converting, open the file in the free Glyph editor — nothing to install, and your files never leave your browser. See Cells & hierarchy and SREF & AREF.

Glyph is made by NANYTE. For where a finished layout goes next, read NANYTE's maskless lithography overview.